If shader file could not be found on loading it crashed, instead added
fallback to default shader!

By default, we look for texture1 for LOC_MAP_SPECULAR and texture2 for
LOC_MAP_NORMAL

Support Universal Windows Platform (UWP):
- Windows 10 App
- Windows Phone
- Xbox One

USE_DEPTH_RENDERBUFFER on OpenGL 2.1

On RPI, after latest drivers update, models were not rendered properly
cause of that...

- Review RPI compilation (core_drop_files not supported)
- Review ImageFormat(), some issues
- GetTextureData() reviewed for RPI

Improve second option to retrieve texture data from fbo...

Still requires some testing...

...while reviewing GetTextureData() functionality on OpenGL ES 2.0

To be more generic and configurable

It should be reviewed more carefully...

Requires some work, distortion shader could be move out of raylib to
example code...

to emulate OpenGL funcionality

Now it works great with reviewed maths

Some other tweaks...

Now it should be coherent with OpenGL math standards

Exposed some raymath useful functions to raylib API

Still shader dependant, locations set should be moved out

Corrected compilation for OpenGL 1.1
Review mesh data uploading to GPU

Moved PBR material loading to example, right decision?

...to avoid possible conflicting symbols