raylib uses spaces between '+' and '-' signs but not between '*' and '/'
signs, it's a chosen convention

LoadOBJ can now load objects with having no texture coordinates or
objects having texture coordinates specified as tuples.

This fix allows GenMeshCubicmap() to create cubic maps having cells of
arbitrary sizes.

This function needs to be redesigned or removed...

It's more educational to go through new material system, so, I decide to
remove this function to avoid students confusion...

To get it, use GetDefaultTexture()

This is a first step toward a bigger project. Some modules could be
ported to header-only to be used as standalone.

Tint color could be applied to colDiffuse... but what's the best way?
Replace it? Multiply by? A point to think about...

It tints all fragments, ignores lighting. Useful for some features like
feedback (damage color, ...).

Scaling normal depth (y axis) makes disappear the specular of
fragments... So I think it can be removed, it is not a very
useful/important attribute.

Draw3DCircle is useful to draw point lights radius.

In standard shader, material glossiness is a value from 0 to 1000 like
in MLT files. So, it doesn't need to be normalized.

- Ambient and lambert lighting added.
- Ambient and diffuse colors linked to standard shader.
- Single light linked to standard shader.
- LoadStandardMaterial() and depending functions added.

Material glossiness is a float type value...

Improved materials

Not tested yet

Depending on mesh data, it can be loaded and default vertex attribute
location points are set, including colors, tangents and texcoords2

if mesh is not loaded properly it breaks the game!

Requires Shader access functions review

- Removed DrawQuad() function
- DrawBillboard() uses DrawBillboardRec()
- DrawPlane() uses RL_TRIANGLES
- DrawRectangleV() uses RL_TRIANGLES, that way, [shapes] module uses
only TRIANGLES buffers.

sin(), cos() functions cached and replaced by float c99 versions sinf(),
cos()

This reverts commit 423a45ac85.