Use COMPAT_ENGINES instead of RenderEngine.use_game_engine for panel poll methods

This mostly affects physics panels. Any engines relying on
RenderEngine.use_game_engine flag to show/hide panels will need to be
updated. The COMPAT_ENGINES technique is how we usually deal with this.
One issue with use_game_engine is that I cannot find a way to set it; it
appears only the BGE can set it. This means (without this commit)
external RenderEngines cannot get rid of the default physics panels.

The RE_GAME flag (the C flag behind use_game_engine) is pretty hacky
and we should look into removing its usage where possible.

BGE: Fix animations when using VBOs

BGE: Fix memory leak in VBO code

BGE code cleanup: Removing RAS_GLExtensionManager.

This class did nothing but print out extensions if they were found.
Instead, the code from bge.logic.PrintGLInfo() is now printed as the
Rasterizer is initialized. This gives better information, and it removes
some GL code from KX_PythonInit.cpp (the PrintGLInfo method now calls
the Rasterizer to print the information).

Differential Revision: https://developer.blender.org/D438

OpenGL/BGE: Remove RAS_StorageIM (glBegin/glEnd rendering of mesh data)

The only use we had for RAS_StorageIM was to render derived meshes using
Blender's mesh drawing. This is now handled as a special case in
RAS_OpenGLRasterizer instead of in RAS_StorageIM.

We are now left with RAS_StorageVA and RAS_StorageVBO. At the moment
vertex arrays are still the default since our vertex array with display
lists implementation is still much faster than our VBO code in a lot of
cases. As we improve our VBO code, we can drop vertex arrays since
Blender's minimum OpenGL version is being bumped up to 2.1, which
supports VBOs.

BGE: Remove RAS_IRasterizer::IndexPrimitivesMulti()

The work that was being done in IndexPrimitiveMulti() is now done by
IndexPrimitive() and we always assume multitexture support.

Fix T45886: cont.deactivate(ActionActuatorInPropertyMode) does not work

Make sure the Action Actuator actually deactivates when given a negative
event while using the property play mode.

Fix for T41536: 2.71 getActionFrame no longer returns frames accurately

We now keep actions around when they are finished playing so scripts can
still get access to information such as the current frame. Playing a new
action in the same layer still overwrites the previous action as before this
commit. Using an explicit KX_GameObject.stopAction() will free the memory. The
action is also freed when the KX_GameObject is freed as before.

Fix T45886: cont.deactivate(ActionActuatorInPropertyMode) does not work

Make sure the Action Actuator actually deactivates when given a negative
event while using the property play mode.

Revert "BGE : KX_VertexProxy support for more than 2 UV channel."

This reverts commit fb0dd596e9a58f095730359a11759c40ea46be44.

This commit reintroduced a deprecated API that we'd rather not see in a
release. A better solution is being worked on.