- Renamed Begin3dMode() --> BeginMode3D()
- Renamed Begin2dMode() --> BeginMode2D()
- Renamed End3dMode() --> EndMode3D()
- Renamed End2dMode() --> EndMode2D()

Depth test disabled for 2D and only used on 3D; consequently LINES vs
TRIANGLES vs QUADS buffers drawing order maters... but blending also
works ok.

- Added CheckCollisionRayBox() function.
- Updated and improved core 3d picking example (currently working as
expected).

Examples have been renamed for coherence with raylib modules and test
examples have been merged into examples folder.

View CHANGELOG for details