When a Font is looked up in the FontLinks table, they have already
been normalised by FontSubstitutes.

So no need to store system_links entries for fonts that appear as keys
in the FontSubstitutes list.

Entries in the list of linked fonts are keyed by the substituted font
name, so need to be looked up by the substituted font name.

msctf: Implement ITfCategoryMgr::RegisterGUID, ITfCategoryMgr::GetGUID and ITfCategoryMgr::IsEqualTfGuidAtom.

Custom actions in the CS3 installer depend on this.

There's no need to waste constants for repeatedly loading the same value.

This extension is a subset of GL_NV_half_float that defines support
for the stream format(same constant), but doesn't define texture
formats or immediate mode entrypoints.

GL_ARB_shader_texture is supported on dx9 ATI cards(and probably dx10
ones too). For Nvidia cards I included a fallback to normal texld.
GL_EXT_gpu_shader4 supports similar texture*Grad GLSL functions, just
with an EXT prefix instead of ARB. For dx9 NV cards we'd have to use
GL_NV_fragment_program2, which supports a texldd equivalent on those
cards.

In SM 1-3 this is just the version, in SM4 this also includes the token count.