Move away from v1.12 as GLFW now requires >= 1.15.

The .travis.yml is getting increasingly ugly. We should maybe consider
creating separate shell scripts for each target..

Specific textures generation code is quite redundant and not flexible for the user, I'm trying to figure out some easy way to allow raylib users to do the same without needing those functions (very specific and shader dependant). RenderTexture loading and Cubemap textures support must be improved.

CMake defaults to generating a Visual Studio build on Windows,
which doesn't involve make. Thus use cmake --build to abstract
that detail away. We already do that in the appveyor.yml.

The install line is a bit hacky: cmake might not be in the search
path when using sudo, thus use "$(which cmake)" to get the path,
sudo doesn't seem to be available on the Travis CI windows
environment, so use $(which sudo) without quotes to expand to
nothing if that's the case...

This reverts commit 214aa0c1b0.

It was develop before, which is no longer used.

Actually, that function should be redesigned...

Considering chars inputs come in UTF8 form!

Same functionality could be achieved using FLAGS... but also considering removing raylib logo animation...

Decided to allow user to provide values directly instead of requiring a Vector2 struct, probably more confortable to use.

 - SetMousePosition()
 - SetMouseOffset()
 - SetMouseScale()

Added SetMouseOffset

- SetMouseScale changed to take in a Vector2.
- Added mouseOffset global which is used in mouse read functions.

utils: declare funopen only on Android

- Didn't set X and Y values correctly.

- Changed mouseScale to Vector2.
- Added SetMouseOffset to change XY of mouseScale.

funopen is only needed on Android, so declare it
only there. This fixes following MinGW build failure:

utils.c:50:7: error: conflicting types for ‘funopen’
 FILE *funopen(const void *cookie, int (*readfn)(void *, char *, int),
       ^~~~~~~
In file included from utils.c:45:0:
/usr/include/stdio.h:586:7: note: previous declaration of ‘funopen’ was here
 FILE *funopen (const void *__cookie,
       ^~~~~~~

Useful for tiling and offset parameters definition.

Added a bunch of useful text management functions.
Consequently, some already available functions like `FormatText()` and `SubText()` has been renamed for consistency. Created temporal fallbacks for old names.
raylib version bumped to 2.3.

Problem aligning provided vertex data to multiples of four, because main buffer is intended to bu used with indexed quads... but also shared with triangles and lines.

Despite issue is corrected, now module loop doesn't work...

Changed parameters order for consistency with LoadFontData() and other functions when an array is passed by parameter and array size is the following parameter.

OpenGL extensions loading could be improved...

Also reviewed rlCheckBufferLimit()