based and less switch-statements-with-hundreds-of-cases based. This shrinks
the x86 asmprinters to about 1/3 their previous size.
Other improvements coming.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29177 91177308-0d34-0410-b5e6-96231b3b80d8