Add RegalPlugin private API for plugin dispatch layers to call back into Regal.
Resolve snappy library Windows compilation warnings.
Improvements for filtering emulation.
Support EXT_framebuffer_object on ES 2
GL_EXT_blend_color, GL_EXT_blend_subtract and GL_NV_blend_square emulation for ES 2.0.
ARB_shader_subroutine completeness for NV_gpu_program5 purposes.
Better log nesting for begin/end, push/pop log pairs.
Regal.cpp codegen tidy-up: reduce casting for default return values.
Regal context sharing for WGL too.
Log the return values of global functions (WGL, etc) in the driver logging stream.
Regal::Marker needs two versions of toString, depending on the relevant extension being emulated.
