previously function used tonumber which returned float
this caused errors in large numbers and resulted in
obj-def-handlers being invalid when retrived from lua tables in c

* Move included json code to jsoncpp subdirectory

This is needed to avoid having to specify the minetest src directory
as a system include when fixing the json includes.

* Fix json includes

They used "", so that the compiler searches the project's directory
first. The result was that when compiling with a system jsoncpp,
the project's own version of json.h was still included, instead of
the system version.

The includes now use <>, so a system location, or one specified with
'-Ilocation' is searched only.

* Fix for jsoncpp deprecated function warning

When compiling with a newer version of jsoncpp (and
ENABLE_SYSTEM_JSONCPP=true), jsoncpp emits a warning
about a deprecated function that minetest uses.

This fallback to std::map & std::set for older compilers

Use UNORDERED_SET as an example in decoration and ore biome sets

Use UNORDERED_MAP as an example in nameidmapping

Fix height check comparison from '>=' to '>'.
Fix getHeight() for schematic decorations to account for
'deco place center y' flag and for how normal placement
sinks schematic 1 node into the ground.

Jungletrees were not being placed at y = 46, y = 47 despite
having an acceptable 16 nodes of height above ground surface.

When the 'flat' and 'trees' flags were moved into mgv6_spflags they
were left in mg_flags in an attempt to support old mgv6 worlds. However
their appearence in mg_flags causes confusion, also, later, old-world
support was found to be broken for mgv6 worlds with 'notrees'.

This commit cleans up the mess and comes a month after a thread warning
of the change, and explaining the required action, was posted in the
news subforum. Only old mgv6 worlds with 'flat' or 'notrees' are
affected, a small minority of worlds, the required action being
correctly setting these flags in mgv6_spflags.

Disable a section of the 'map settings manager' unit test which is to
be changed as it is causing problems for pull requests.

l_request_insecure_environment didn't ignore all whitespace in the
secure.trusted_mods config option.

Replaces std::remove with std::remove_if and the isspace function.

For consistent horizontal sprite structure when seen from front and back
Fix code style

When a CavesNoiseIntersection tunnel intersects a river place biome
'riverbed' nodes in tunnel entrance instead of biome 'top' nodes.

To fix GCC 6.1.1 compilation warning:
'assuming signed overflow does not occur when assuming
that (X - c) > X is always false'

Fix #4137 for rollback.cpp as well.

Fixes #4137

Modifications by est31: grammar fixes in doc + error messages and
a little style fix, no functional change.

Also update cinematic mode's description to include mouse

Since the creation of minetest, it had no window icon on X11.
Now we have one.

The misc/minetest-xorg-icon-128.png file is a rendering of the
misc/minetest.svg file with inkscape, created with something like:

inkscape -z -e misc/minetest-xorg-icon-128.png -w 128 -h 128 misc/minetest.svg

The "testStartStopWait" unit test is unreliably failing on mac,
for some time already. See bug #3786.

Having the unittest fail unreliably doesn't help anybody but mostly
inhibits the main feature of travis builds: to test PRs for regressions.

Therefore, disable the specific unit test for until bug #3786
is fixed.

The source used a hodge-podge of different combinations of different
macros to check for linux: 'linux', '__linux', '__linux__'.

As '__linux__' is standard (Posix), and the others are not, the source
now uniformly uses __linux__. If either linux or __linux are defined,
it is made sure that __linux__ is defined as well.

It seems that various different devices register as
Joysticks on linux, and their presence has caused
lots of confusion amongst minetest users.

Therefore, disable the joystick feature.

Closes #4261
Closes #4221

Move version information into the window caption.

On popular player request.

Fixes #4209.

This commit refactors the majority of the Mapgen settings system.
- MapgenParams is now owned by MapSettingsManager, itself a part of ServerMap,
  instead of the EmergeManager.
- New Script API functions added:
    core.get_mapgen_setting
    core.get_mapgen_setting_noiseparams,
    core.set_mapgen_setting, and
    core.set_mapgen_setting_noiseparams.
- minetest.get/set_mapgen_params are deprecated by the above new functions.
- It is now possible to view and modify any arbitrary mapgen setting from a mod,
  rather than the base MapgenParams structure.
- MapgenSpecificParams has been removed.

- Move mapgen creation logic out of EmergeManager and into Mapgen
- Internally represent mapgen type as an enum value, instead of a string
- Remove the need for a MapgenFactory per mapgen

X11 headers are not always in expected locations, add them to include list.

Modifications by est31: indentation fixes, commit message improved

Fixes #4251

Reduce spread from 96 to primes 61 and 67 (either side of 64)
Prime spreads help to keep 3D noise periodic features unaligned
'cave width' 0.2 to preserve tunnel width
Reduce octaves to 3 to improve network structure

Deprecate get_look / set_look pitch / yaw

- Generalise node names to c_wall and c_alt_wall
- Remove 'mossratio' and instead disable alt_wall loop if
  c_alt_wall == CONTENT_IGNORE
- Use one generalised 3D noise for alternative wall nodes and in
  mgv6 create moss distribution similar to the previous

- Rename rarity noise to density noise and enable the option of multiple
  dungeons per chunk determined by the value. Recreate previous distribution
- Add parameters for min and max rooms per dungeon
- Add dungeon y limits

- Integrate river water properly

Generalisation is needed now that we have sandstone and desert stone
dungeons by default and can choose any node for alternative structure.
The current code is based around cobble dungeons with mossycobble
alternative nodes, the 2 noises controlling the alternative nodes
are based on wetness.

Enabling multiple dungeons per chunk with definable number of rooms
allows the option of very dense and complex underground structures
that could interconnect to create megastructures.
Y limits are added to be consistent with other mapgen elements, and
enable locaton of dungeon or megastructure realms as part of our
'stacked realms' philosophy.

Texture packs have no way to know what nodes are available, so this shouldn't be a error message.

 - Fix unused c_sand member warning in Valleys Mapgen
 - Fix some code style
 - Make some std::string params const ref