- Mesh, Shader, Material structs have been reviewed to minimize size when passed by value, all required code has been reviewed.
 - GetCollisionRayModel() reviewed to avoid pointer, not required because model is not modified inside the function
 - UnloadMesh() reviewed, pointer not required
 - CheckCollisionRay*() parameters name reviewed

* Fix loading multiple animations from .iqm file

* Fix memory leak in models_animation example

* Added export instructions to the animation example

* use raylib free

* include <stdlib.h> to appease the travis CI gods

* replace tabs with spaces

When using FormatText() several times in same function, returned string is static and so, the same is returned, resulting in failures on shader loading.

Redesigns, deletes and renames

Also noted authors propertly on contributed examples

Added walls collision check

Some tweaks

Issue was related to vertex tangent attibutes not uploaded to GPU, a quick solution was implemented for new vertex attributes loading for already existing meshes... I don't like it specially but it will work for now.

Multiple functions added and some reviewed to adapt to the new multi-mesh, multi-material and animated models.

Actually, that function should be redesigned...

To generate 2D polygonal shape

This commit implements a big update of rlgl module, intended to optimize some parts. This change could break some code bases... hopefully not, but it could.
The BIG changes to the module are:
 - Replaced LINES-TRIANGLES-QUADS buffers by a single one, now all vertex data is accumulated on a single buffer and managed with registered draw calls. LINES-TRIANGLES-QUADS could be used the same way as before, rlgl will manage them carefully. That's a big improvement of the system.
 - Support multi-buffering if required. Just define MAX_BATCH_BUFFERING desired size (currently set to 1 batch). Should be enough for most of the situations.
 - Removed temporal accumulative buffers for matrix transformations, now transformations are directly applied to vertex when on rlVertex3f()
 - Reviewed rlPushMatrix()/rlPopMatrix() to be consistent with OpenGL 1.1, probably I should remove that ancient behaviour but... well, it was not consistent and now it is.
 - Minor tweaks: LoadText(), I broke it in last update... also multiple comments reviewed.
 - TODO: MAX_BATCH_ELEMENTS checking should probably be reviewed... done some tests and it works but...

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

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