1. Split setValueName into two separate functions, one that is only used
     at function scope and doesn't have to deal with duplicates, and one
     that can be used either at global or function scope but that does deal
     with conflicts.  Conflicts were only in there because of the crappy old
     CFE and probably should be entirely eliminated.
  2. Insert BasicBlock's into the parent functions when they are created
     instead of when they are complete.  This effects name lookup (for the
     better), which will be exploited in the next patch.

llvm-svn: 14787