Split generated asm mnemonic matching table into a separate table for each asm variant.

This removes the need to store the asm variant in each row of the single table that existed before. Shaves ~16K off the size of X86AsmParser.o.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187026 91177308-0d34-0410-b5e6-96231b3b80d8