- All variables are initialized on declaration, some arrays were not properly initialized
- Static array buffers require memset() for re-initialization on every function call
`RLGL.State.vertexCounter` is a generic counter and it's reused for all `rlRenderBatch`, actually, once render batch is filled, required vertex count is provided through the draw calls, so, the total accumulated count of vertices is not directly registered inside the rlRenderBatch.
`RLGL.State.vertexCounter` keeps that count but one possible improvement(?) could be moving the `vertexCounter` inside `rlRenderBatch` to always keep a register of the total accumulated vertices in that batch (despite that info is provided by the accumulated `draws[i].vertexCount`.
Simplifying, `RLGL.State.vertexCounter = SUM(draws[i].vertexCount)`
The decision to move the counter out of `rlVertexBuffer` is to keep only the data that I think should belong to `rlVertexBuffer` and make it more generic, aligned with raylib `Mesh` structure.
The decision to not add it to `rlRenderBatch` is because it could contain multiple `rlVertexBuffer` and it would be confusing (because it would only register the count of the last filled one).
Instead of registering vertex texcoords and colors on every call, we keep the last defined value and we record everything on `glVertex*()`. Actually that behavior is aligned with OpenGL 1.1 standard.
Note that `extern "C"` calling convention only affects objects that need to be seen by the linker, in our case only functions... but it would also be required by global variables exposed, if any.
