Removed functions from rlgl module.

Simplified some parts and reviewed for a correct computation of matrices, considering stereo render view/projection per eye transformations

shaders_rlgl_mesh_instanced -> shaders_mesh_instancing

* adds DrawTexturedPoly with example

* the actual example ... ahem

* moved DrawTexturePoly to textures function and example
NB function name changed to fit with other DrawTextureXXX functions
(no "d" )

Co-authored-by: codifies <you@example.com>

* Fix some warnings in examples.

* cleanups from review

Co-authored-by: Jeffery Myers <JefMyers@blizzard.com>

- Some rlgl functions have been moved to core
 - Some functions have been made internal to rlgl
 - rlgl functions prefixed with rl*()

Vr simulator has been moved to core module and completely redesigned. Now user is in charge of stereo-render fbo and also in full control of distortion shader. Code is a bit more complex but better aligned with other raylib examples.

Co-authored-by: Simon <simon@frithrah.com>

* Implement a load values from accessor function.
Added some more value types for the different GLTF attributes.
Fixed crash when loading animated triangle.

* Split GLTF model loading into separate functions for readability.

* Fixed the already working models that I broke when introducing GLTFReadValue.
Improved the example for gltf models to be able to switch between a few models.

* Removed license from screen. It is pu inside a license file anyway.

* Small improvements on the naming of functions
Removed (*model). and replaced it with model->

Some enums values have been renamed to be more consistent and also provide a more detailed description:
 - ShaderLocationIndex:    LOC_VERTEX_POSITION -> SHADER_SHADER_LOC_VERTEX_POSITION
 - ShaderUniformDataType:  UNIFORM_VEC2 -> SHADER_UNIFORM_VEC2
 - MaterialMapType: MAP_ALBEDO -> MATERIAL_MAP_ALBEDO
 - PixelFormat: UNCOMPRESSED_GRAYSCALE -> PIXELFORMAT_UNCOMPRESSED_GRAYSCALE

* Added bone binding to whole mesh and not only set vertices.
+ Also added missed setting of the animation count.
+ Removed double ; on one line

* Added more of the gltf sample models

https://github.com/KhronosGroup/glTF-Sample-Models
We need to make it working for all of them.

* Binding to initial bind pose added.

* Fix cube disappearing bug because lerpPercent could be Inf.

* Fixed for rigged figure also

RENAMED: CubemapLayoutType and NPatchType

Updates skybox demo to show how to do both HDR and non HDR skyboxes

Co-authored-by: Jeffery Myers <JefMyers@blizzard.com>

* Fixing typecast warnings generated by visual studio 2019 in examples.

* Changes to fixes based on feedback

Co-authored-by: Jeffery Myers <JefMyers@blizzard.com>

Mostly typecasts, and some int to unsigned short changes, and including the windsock 2 library in the examples.

Co-authored-by: Jeffery Myers <JefMyers@blizzard.com>