Don't use unsigned char for alignments in TargetData. There aren't

Don't use unsigned char for alignments in TargetData. There aren't
that many of these things, so the memory savings isn't significant,
and there are now situations where there can be alignments greater
than 128.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110836 91177308-0d34-0410-b5e6-96231b3b80d8