primitives: fix compile warning exposed when ASM and instrincs are both disabled

--HG--
branch : stable
common: disable MSVC warning that is exposed when compiling without primitives

--HG--
branch : stable
cpu: move ASM fallback functions out of vec-primitives.cpp

This fixes link errors when ASM and vector primitives are both disabled

--HG--
branch : stable
api: give structs the same name as their typedef

This allows them to be forward-decl'd.

--HG--
branch : stable