Combine texture_overrides.txt and sections of lua_api.txt

* Update README.txt

As of Ubuntu 16.10, libpng12-dev is replaced with libpng12-0, since libpng12-0 is available in 16.04 repositories, I think that needed to be changed.

Also I changed 'git-core' to 'git' for fedora users, keep it consistent with the ubuntu/debian instructions.

* Update README.txt

Instead of trying to manually parse the output of 'git show' which can be different across different git configurations, properly use the 'git rev-parse' command that is intended for this purpose.

This little update is due to a packaging problem when uploading on play store. They don't permit to re upload an APK with same version code.
This case was a fail on openssl packaged version which was old and rejected by Google but they don't remove the APK then i should increase the version code to permit having it on play store

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

Recommend mod screenshot size in lua_api.txt
Adjust displayed screenshot size of texture packs
Document texture pack files in lua_api.txt

core.check_player_privs accepts as first argument a name or player object, but just tested for a string.
This caused crashes inside builtin, when being passed any unexpected types.

This provides a better (duck-typing like) test, better error reporting.

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

Use the setting "profiler.load" to enable profiling.
Other settings can be found in settingtypes.txt.

* /profiler print [filter] - report statistics to in-game console
* /profiler dump [filter] - report statistics to STDOUT and debug.txt
* /profiler save [format [filter]] - saves statistics to a file in your worldpath
	* txt (default) - same treetable format as used by the dump and print commands
	* csv - ready for spreadsheet import
	* json - useful for adhoc D3 visualizations
	* json_pretty - line wrapped and intended json for humans
	* lua - serialized lua table of the profile-data, for adhoc scripts
* /profiler reset - reset all gathered profile data.
	This can be helpful to discard of any startup measurements that often spike during loading or to get more useful min-values.

[filter] allows limiting the output of the data via substring/pattern matching against the modname.

Note: Serialized data structures might be subject to change with changed or added measurements.
	csv might be the most stable, due to flat structure.

Changes to the previous version include:

* Updated and extended API monitoring
* Correct calculation of average (mean) values (undistorted by idleness)
* Reduce instrumentation overhead.
* Fix crashes related to missing parameters for the future and occasional DIV/0's.
* Prevent issues caused by timetravel (overflow, timejump, NTP corrections)
* Prevent modname clashes with internal names.
* Measure each instrumentation individually and label based on registration order.
* Labeling of ABM's and LBM's for easier classification.
  Giving several ABM's or LBM's the same label will treat them as one.
  Missing labels will be autogenerated based on name or registration order.
* Configurable instrumentation and reporting. Skip e.g. builtin if you don't need it.
* Profile the profiler to measure instrumentation overhead.

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

Currently translated at 100.0% (887 of 887 strings)

Currently translated at 89.6% (795 of 887 strings)

Currently translated at 55.8% (495 of 887 strings)

Currently translated at 59.0% (524 of 887 strings)

Currently translated at 91.2% (809 of 887 strings)

Currently translated at 75.1% (667 of 887 strings)

Currently translated at 31.5% (280 of 887 strings)

Currently translated at 32.2% (286 of 887 strings)

Currently translated at 74.1% (658 of 887 strings)

The package docs for the git-core Ubuntu package in all supported
Ubuntu versions, including 12.04 say:

This is a transitional dummy package.  The 'git-core' package has been
renamed to 'git', which has been installed automatically.  This git-core
package is now obsolete, and can safely be removed from the system if no
other package depends on it.

Fixes #4109

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