Reviewed by Leslie

EXP-997 FIX -- Significant FPS degradation in 2.8.0 Beta on Mac equipped ATI video card

* Disabled VBO's on mac to avoid stalls in renderer
* Placed valid data into the padding between triangles in the vertex buffer to remove uninitialized craziness
* Removed invalid rendering checks causing GL errors in debug mode

Reviewed by davep

SH-2031 Fix for shadow render targets using inappropriate shader for occlusion culling resulting in objects popping in and out of the shadow map.

SH-2031 High risk changeset, but potentially high reward.  Addresses frame stalls in renderer by never using the fixed function pipeline if shaders are available.

SH-2038 Disable usage of stream vbo on mac and make flexi's use stream vbo if stream vbo disabled (effectively disables usage of vertex buffers for flexible objects on mac)

SH-2038 Fix for some compiler errors from the apple tweaks -- also add a fence API (disabled for now).

Options tab.

reviewed by Leslie

Drag and drop for LLFolderView now handles the empty mFolders case.

Turns out that BaseHTTPServer.HTTPServer turns on that flag by default, which
causes freeport() to fail (on Windows only?), happily instantiating multiple
servers on the same port. Change known instances, fix freeport() docstring to
highlight the issue. Add freeport() unit tests to verify expected behavior.

and muck with the "About Land" Options tab one more time.