swift234

Fix several bugs in the emission of metatype references.

In particular, fix a bug where DREs that refer to types were
always given trivial reps because we were trying to emit the
metatype's metatype.  This in turn exposes a number of bugs,
including a typechecker bug (where GetMetatypeExpr bases
weren't converted to r-values) and a bug where MREs that
refer to types were always assumed to produce trivial reps.

Swift SVN r3095