Use SSE intrinsics instead of GCC specific __builtin functions

The __builtin_ia32_loadups and __builtin_ia32_storeups functions are GCC
specific and are not supported by compilers like LLVM. Instead use the more
often supported SSE intrinsics.
Merge pull request #2 from ecsv/llvm

Use SSE intrinsics instead of GCC specific __builtin functions
Define binary helper functions used in pure C TexLoad*
Use pure C version of TexConv.h from glide64mk2

The asm versions seem to fail to build on OpenBSD when PIC is enabled on i386
because more registered are used in the asm part then there are available.
Use pure C version of TexLoad4b.h from glide64mk2

The asm versions seem to fail to build on OpenBSD when PIC is enabled on i386
because more registered are used in the asm part then there are available.
Use pure C version of TexLoad8b.h from glide64mk2

The asm versions seem to fail to build on OpenBSD when PIC is enabled on i386
because more registered are used in the asm part then there are available.
Use pure C version of TexLoad16b.h from glide64mk2

The asm versions seem to fail to build on OpenBSD when PIC is enabled on i386
because more registered are used in the asm part then there are available.