No model available, this example should probably be redesigned...

Oculus API has changed so much that it has no sense to keep this example here... it was funny to test it in the past...

This change allows rlgl.h usage as independent single-file header-only module... still some tweaks required, like removing GLAD dependency... required extensions could be manually loaded!

Also removed shader_distortion.h, embedded in rlgl.h

Fixes: c3b948b1 ("Replaced skybox HDR image")

Replaced old dwarf model

Note that HDR exposured possibilities are not used on this example...

Replaced by medieval 3d assets

It seems TCC was not casting correctly int values to float in some
specific situations

src/core.c does explicitly skip including <camera.h> on Android
and tests fail. Therefore skip these failing tests.

Closes #507.

Currently, if:
* GCC doesn't supports -no-pie: Build error
* GCC supports -no-pie
    * GCC is not configured with --enable-default-pie: No-op
    * GCC is configured with --enable-default-pie:
            Slightly worse performance because we still generate -fpie code
            (-pie affects linker, -fpie affects compiler)

So instead of probing for existence of -fno-pie -no-pie, remove it altogether.

Fixes #540: Build breakage on Debian 8 with gcc 4.9.

Review raylib_icon resource

- Preparing MP3 files support
- Jumped version to raylib 2.0-dev (too many breaking changes...)

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

- Some examples tweaks
- Reviewed ImageFormat()
- Use float for text fontSize

Just added a fallback in the meantime...

- Added Vector3OrthoNormalize() to raymath.h - not sure if it is correct
- Implemented MeshBinormals() - Mesh struct has not a place for them...
- Updated model_material_pbr example - tested but not working on my GPU
(old Intel HD), actually, it never worked on it...

Changes made based on commentary in pull request 513