texture() doesn't exist in glsl 100, it must use texture2D().

Shaders come in two flavours:
- shaders/gl330: OpenGL 3.3+ (Windows, Linux, OSX)
- shaders/gles100:  OpenGL ES 2.0 (Android, RPI, HTML5)

- Camera system moved to a separate module [camera.c]
- WIP: Added customization functions for camera controls
- Added custom shaders support on batch drawing
- Complete redesign of textures module to support multiple texture
formats (compressed and uncompressed)