More cleanup of the type traits implementation.

1) Moved the completeness checking routine above the evaluation routine
   so the reader sees that we do in fact check for complete types when
   necessary.
2) Remove the FIXME comment about not doing this.
3) Make the arguments to the evaluate function agree in order with those
   to the completeness checking function.
4) Completely specify the enumerators for the completeness checking
   function rather than relying on a default.
5) Remove a check for the Borland language to only require complete
   types in a few places. Borland's own documentation doesn't agree with
   this: some of the previously unspecified traits *do* require
   a complete type, some don't.
6) Correctly split the traits which do not require complete types from
   those that do, clarifying comments and citations to the standard or
   other documentation where relevant.

llvm-svn: 130641