Function has been reviewed to avoid any direct OpenGL call and use rlgl functionality, also, GenDrawCube() has been replaced by the internal batch system with DrawCube().
WARNING: rlEnableTexture() call must be issued after enabling the current framebuffer when using batch mechanism because it includes a set of security checks to avoid batch overflow and push/pop matrix operations.
This redesign allows more flexibility when creating RenderTexture and a simplification (and hopefully removal) of `GenTexture*()` functions, that should not belong to this model but the user code, due to the use of custom shaders.
Also, this new API opens the door for a possible GBuffers type and advance rendering possibilities...
Some functions of the API have been also simplified or even removed.
rlgl module can be used as an standalone library, so, a version for the library has been added: v3.1.0, matching current raylib version.
Before deleting certain objects, they must be detached from their parents. That's the case for shader objects after linkage to shader program and also for the texture/cubemaps/renderbuffers attached to framebuffers. If objects are deleted before detached, they are kept in memory to avoid accessing deleted data.
rlBlendMode() has been added to rlgl to be used on BLEND_CUSTOM. This functionality is exposed to advance users.
In any case, new blending modes could be added if required.
Most warning were related to types conversion (casting required) and unsigned/signed types comparisons.
Added preprocessor directives (_CRT_SECURE_NO_DEPRECATE; _CRT_NONSTDC_NO_DEPRECATE) to avoid warnings about unsafe functions, those functions are safe while used properly and recommended alternatives are MS only.
Some external libraries still generate warnings.
Created RenderBatch type and related functions to allow rlgl users creating custom and separate render batches and not only rely on one internal render batch.
This feature has not been exposed on raylib yet because it implies some breaking changes. Right now a custom RenderBatch is just used internally in rlgl.
