swift234

Peel off almost all of the uses of MetaTypeExpr, replacing 
them with uses of TypeExpr instead.  The remaining uses of 
MetaTypeExpr (which will be renamed soon) are places where we
are applying the ".dynamicType" virtual property to an expression.

Unadorned uses of types in code, e.g. the Int in "Int.self" are
now represented with TypeExpr.

One unfortunate travesty that doing this work revealed is that we
are extremely sloppy and terrible about maintaining location information
in implicitly generated decls, and our invariants vary quite a bit.  This
is really horrible, but I'm not sure whether I'll go fix the hacks or not.

This patch perpetuates the existing crimes, but makes them more visible.

NFC!




Swift SVN r16646