Previously, the server called FATAL_ERROR when a Lua error occured.
This caused a (mostly useless) core dump.
The server now simply throws an exception, which is caught and printed before
exiting with a non-zero return value.
This also fixes a number of instances where errors were logged multiple times.

This allows the player to toggle continuous forward with a key (F by default),
so we don't have to hold down the forward key endlessly.

Increase default from 6 to 16 to help with mgv7 and mgfractal
Large-scale or alternative mapgens can result in a lowland spawn point not
being found, causing a spawn at (0, 0, 0) possibly buried underground
The max height is now settable to allow correct player spawn
in any mapgen or when using custom noise parameters

Use this macro to disallow copying of an object using the assignment
operator or copy constructor.  This catches otherwise silent-but-deadly
mistakes such as "ServerMap map = env->getMap();" at compile time.

If so desired, it is still possible to copy a class, but it now requires
an explicit call to memcpy or std::copy.

-> Put access to time variables under the time lock.
-> Merge both time locks, there is no point to have two locks.
-> Fix the lock being released too early in Environment::setTimeOfDay
-> Add serverside getter so that you don't have to get
	the environment if you only have the server

Also fix a potential seed truncation issue on platforms where the
range of ptrdiff_t (the underlying type of lua_Integer) is too small.

abort() doesn't benefit from the high level abstractions from FATAL_ERROR.

Remove outdated loglevel list from a l_util.cpp comment,
and rather point to the updated code.

Fixes #3280

- Disabled by default (except players)
- Fixes #2984

Previously, the invocation of Logger::addOutput(ILogOutput *out) led to
an out of bounds write of the m_outputs vector, resulting in the
m_silenced_levels array being modified.

Fortunately, the only caller of that method was android system logging,
and only since a few commits ago.

Complete set of parameters for each of mandelbrot and julia sets
The julia set structure often needs different iterations and scale

Fixes #3291

Thanks to @arpruss for reporting the bug, and suggesting the fix.

Also, remove trailing whitespaces.

Previously, xgettext failed to resolve the dynamic call.
Thanks to @JakubVanek for pointing this out.

-> Get rid of Logger::logToSystem and use normal downstream output system for android instead

-> Give the downstream output system more information: enrich the log function of ILogOutput
	with information and add ICombinedLogOutput for easier use.

-> Make Logger::getLevelLabel() static and public so that it can be used by downstream log output.

-> Add g_ and m_ prefixes where required

* Add key settings to setting table and ignore them later
  This way they are added to the auto-generated minetest.conf.example
* Add flags type
* Add input validation for int, float and flags
* Break in-game graphic settings into multiple sections
* Parse settingtpes.txt in mods and games
* Improve description for a lot of settings
* Fix typos and wording in settingtypes.txt
* Convert language setting to an enum

Thanks to SmallJoker for pointing this out.

fixes https://github.com/minetest/minetest_game/issues/537

Index more columns in the action table of the rollback DB to improve the performance of /rollback_check

Flushes the buffer of rollback actions that wait to get saved in two more situations:

1. Flushes in the destructor of the rollback. This makes the server not
forget the last < 500 rollback entries when it shuts down.

2. Flushes the rollback when /rollback_check is invoked. This is neccessary
as otherwise it leads to confusion if users want to test the rollback functionality
by placing a node and then executing the check on it, or if the actions were
very recent out of other reasons.

- Fix thread name reset on start()
- Fully reset thread state on kill()
- Add unittests to check for correct object states under various circumstances

Add findLiquidSurface() function to mapgen.cpp
Update lua_api.txt