Remove deprecated jASSUME from pcsx2 core. It is still used in some plugins
Use __builtin_unreachable where possible for non-msvc
Merge pull request #209 from xsacha/jASSUME

Remove deprecated jASSUME from pcsx2 core. It is still used in some plugins.

[I should note that this may change the performance of the devel target on msvc as jASSUME was compiling to __assume on devel and release while pxAssume only compiles to __assume on release]