SH-2507 Shave some unused/redundant varying state and make the max texture index debug setting rebuild shaders to use no flow control when set to 1 or lower

SH-2244 changes to run in a core context on AMD hardware without generating deprecation or performance warnings

SH-2244 Fix for crash when transparent water disabled (silently ignore setting when basic shaders enabled)

SH-2244 Vertex buffer cleanup, fix for bad vertices in rigged attachments, added "RenderUseVAO" debug setting to control whether or not to use VAO's in non-core GL profiles.

SH-2244 Fix "RenderGLCoreProfile" actually make a core profile context and modify viewer to run under said context without generating errors.