USE_DEPTH_RENDERBUFFER on OpenGL 2.1

Not tested, could have errors

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

Have SetShaderValue(i) take a const pointer

Could correct possible issues on OpenGL 1.1

C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin>dumpbin.exe
D:\GitHub\raylib\release\libs\win32\msvc\raylib.dll /DEPENDENTS

Microsoft (R) COFF/PE Dumper Version 14.00.24215.1
Copyright (C) Microsoft Corporation.  All rights reserved.

Dump of file D:\GitHub\raylib\release\libs\win32\msvc\raylib.dll

File Type: DLL

Image has the following dependencies:

KERNEL32.dll
glfw3.dll
OpenAL32.dll

Summary

4000 .data
1000 .gfids
23000 .rdata
5000 .reloc
1000 .rsrc
68000 .text
1000 _RDATA

Added support for raylib DLL building on MSVC

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

Corrected issue with RPI_CROSS_COMPILE

Added support FreeBSD

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

Still requires some testing...

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

Hopefully new videos comming soon...

- Added new function: GenImageColor()

ImageDraw() should be reviewed... specially alpha blending...

Now it works! :)

Integrate Develop branch

Integrate Develop branch