Fix for linux (and likely other platform) shutdown crash from mismatched alloc/free in VBOPool client data

Reviewed by Graham

Reviewed by Graham

Crashfix; Change llassert_always to llassert + llwarns. This way users don't get disruptive crashes.

MAINT-616 Factor out calls to glGenFoo where possible, add setting to control synchronizing strategy WRT occlusion queries, add experimental transform feedback driven LoD update

MAINT-616 Different VBO Pooling scheme -- populate VBO pool with buffers that are likely to be requested, but never reuse a previously used buffer.

Cleaning up miscellaneous differences between the pathfinding repository and the latest viewer-development.

SH-2908 Rework indexed texture rendering to use a uvec4 instead of a float for texture indices in the data stream.  Also rework gl_FragColor overrides to not collide with some odd driver implementations.

SH-2794, resolved merge conflict and corrected logic in LLVertexBuffer::determineUsage() to work the way it used to.

* Cleaned up vertex buffer allocation to guarantee allocation and deallocation using the same allocation methods from the same pools.
* Added new shader feature for atmospheric helpers in the absence of lighting.

Reviewed by davep.

SH-2565 Move resetVertexBuffer operation to a consistent location (also avoid redundant resetting of vertex buffers on detail switches).  Change assertion to a warning with count info.  Fix bytes pooled debug display.  Remove unused static vertex buffer.

SH-2794 Fix for bad textures on some hardware when vbo mapping disabled (always use GL_STREAM_DRAW as the usage hint when mapping is disabled as geometry will be uploaded again and again)

SH-2700 Fix for random black textures due to texture index out of bounds.  Also change shader to show bright pink on index out of bounds and add assertions to help prevent this sort of bug in the future.

SH-2428 Make GCC 4.4 happy by using LLVector4a striders with LLAlphaObject subclasses -- also vectorize particle VBO updates

SH-2447, SH-2525, SH-2276 Strip out defunct global illumination code, add accounting for how much memory is taken up by LLRenderTarget, fix crash on login in bindGLIndices (work around driver bug that doesn't respect VAO state WRT to index buffers), remove some unused render targets, remove some unused shaders, make it possible to run a fullscreen session