Removed usage of inbuilt asm. Using compiler code generation instead.

The inbuilt asm requires masm syntax support. Currently the project was
only ever converted to use MMX optimisations in MSVC. Since these are
extremely dated then SSE2 code will be generated by using compiler
optimisatios instead. To return to using inbuilt optimisations simply
redefine  OC_X86_ASM.