Some internal defines have been exposed in config.h

* Implemented DrawTextureTiled()

* Example added

* Fix bug #1270

Added an argument to the shader in order to flip the texture

* Fix Bug #1270

* Fix bug #1270

Probably there is a better way to do this but this is a temporary solution for backward compatibility

After multiple tests and lot of redesign, current implementation is the fastest one. It also considers several fast-paths for maximum speed!

WARNING: Some functions ADDED and some RENAMED:
- RENAMED: Fade() -> ColorAlpha() [Added #define for compatibility]
- ADDED: ColorAlphaBlend()
- ADDED: GetPixelColor()
- ADDED: SetPixelColor()

Trying a new optimization approach, some additional functions added, they will be probably exposed soon.

Despite all the effort put on function optimization, dealing with alpha blending is complex, considering src and dst could have different pixel format...

Optimized to avoid ImageCrop() calls, now we define the source image rectangle and we just copy that data over the new canvas.

Always using RGBA for now.

Further optimization, moving data line-by-line
Old optimization left for reference

Using ImageResizeCanvas()

Now uses GetImageAlphaBorder()

Avoid GetImageData() retrieval and free

Added several optimized options for future reference (if required)