[X86][I86,I186,I286,I386,I486,PPRO, MMX]: Adding full coverage of MC encoding...

[X86][I86,I186,I286,I386,I486,PPRO, MMX]: Adding full coverage of MC encoding for the I86, I186, I286, I386, I486, PPRO and MMX isa sets.<NFC>

NFC.
 Adding MC regressions tests to cover the I86, I186, I286, I386, I486, PPRO and MMX isa sets.
 This patch is part of a larger task to cover MC encoding of all X86 ISA Sets.
 Started in revision: https://reviews.llvm.org/D39952

Reviewers: zvi, RKSimon, AndreiGrischenko, craig.topper
Differential Revision: https://reviews.llvm.org/D40879

Change-Id: I231a35861611bfd3d23c74cc59507373f021a629
llvm-svn: 322544