Teach the foldable tables about 128-bit AVX instructions and make the

alignment check for 256-bit classes more strict. There're no testcases
but we catch more folding cases for AVX while running single and multi
sources in the llvm testsuite.

Since some 128-bit AVX instructions have different number of operands
than their SSE counterparts, they are placed in different tables.

256-bit AVX instructions should also be added in the table soon. And
there a few more 128-bit versions to handled, which should come in
the following commits.

llvm-svn: 139687