In addition protect against their use on 32 bit and the use of [ABCD]H
together with a REX prefix on 64 bit.
This assumes that the customOp parameter of WriteREX and operandReg of
OpArg always are registers, and thus needs to give something valid to
WriteREX when that is not the case (WriteShift).
In addition to the patch i sent to the ML, there are a few changes to the
error reporting(mostly whitespace).
git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@7202 8ced0084-cf51-0410-be5f-012b33b47a6e