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.

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

Also reviewed rlCheckBufferLimit()

To draw only in defined area of the screen
ADDED: BeginScissorMode(), EndScissorMode()

Corrected bug on ImageDrawRectangleLines()

REVIEWED: ImageDrawRectangle()
ADDED: ImageDrawRectangleLines()

By default, internal white texture was used to draw most of the shapes; some time ago, support for white font character from default internal font was added. That way, all basic drawing (shapes, text) could be performed without a texture change and in a single drawing pass.

Now, we move a step further and we allow configuring the texture (and rectangle) used to do the shapes drawing.

text:     IsEqualText() -WIP-
audio:  SaveWAV()
audio:  ExportWaveAsCode()
textures:  ExportImageAsCode()

RENAME: GetLastWriteTime() to GetFileModTime()

- Added a function to get the last write time of a file. I used this so I can reload files or resources if the time since they were last loaded changes.

The prototype of GenImageFontAtlas() in the main raylib.h header has a set of swapped parameter names.
Going through the usage of the function within raylib itself, it appears as if the correct order is:
1) charsCount
2) fontSize

However, it's exposed to the world as the other way around, which may cause some major confusion.

REVIEW: Reorganized global variables for consistency
ADDED: GetWindowHandle() to get native window handle
ADDED: GetDirectoryFiles() to get files list for a DIR

Previously, if <raylib.h> was #included prior to another header that
defined bool, the compilation would fail.
This is e.g. the case for <perl.h> and <objc/objc.h> which both fall
back to the <stdbool.h> if C99 is available.

The following commit includes <objc/objc.h> in src/core.c, which causes
the same problem.

Avoid this by checking for C99 bool like we already do for C++'s.

- Using same idea as SetWindowMonitor to take in a index with 0 being the primary monitor.

- Fixed tabs used instead of 4 spaces

- Get number of monitors
- Get size, physical size and name of primary monitor. Could pass monitor id instead not sure.

REVIEWED: ExportImage()
REVIEWED: ExportMesh()
ADDED: ExportWave()
REMOVED: Internal funcs: SavePNG(), SaveBMP()

NOTE: These changes break the API (parameters order)

Useful for bitmaps pixelated fonts where anti-aliasing is not desired!
Change also enables additional font generation mechanisms in a future (cleartype, hinting...).

Added support form vertical and horizontal 3-patches.
Corrected the distortion caused when destRec size is smaller than 4x4. Now even 1x10 or 0x0 sizes are drawn correctly.

Added NinePatch struc definition and function prototype.

Still a work in progress but it already works...
Current riqm API could be simplified...

Vector4 -> Quaternion
Texture2D -> Texture
RenderTexture2D -> RenderTexture
Camera3D -> Camera
SpriteFont -> Font