[x86] add fake scalar FP logic instructions to ReplaceableInstrs to save some bytes

We can replace "scalar" FP-bitwise-logic with other forms of bitwise-logic instructions. 
Scalar SSE/AVX FP-logic instructions only exist in your imagination and/or the bowels of 
compilers, but logically equivalent int, float, and double variants of bitwise-logic 
instructions are reality in x86, and the float variant may be a shorter instruction 
depending on which flavor (SSE or AVX) of vector ISA you have...so just prefer float all 
the time.

This is a preliminary step towards solving PR6137:
https://llvm.org/bugs/show_bug.cgi?id=6137

Differential Revision:
https://reviews.llvm.org/D26712

llvm-svn: 287122