Reorganize things a bit in preparation for rewrite. Although this looks

like a lot, its really only two changes:

1. Move stuff that should be private to .y out of the .h file.
2. Make all semantic values pointers.

This cleans up the silly destroy methods and changes them to delete. It
also moves the TypeInfo and ValueInfo classes into the .y where we can
modify them more readily because they have no clients any more.

This shouldn't result in any functional changes in llvm-upgrade.

llvm-svn: 33211