In objc mode, every identifier in a cast expression was using doing a

type looking using getTypeName() and every property access was using
NextToken() to do lookahead to see if the identifier is followed by
a '.'.  Rearrange this code to not need lookahead and only do the
type lookup if we have "identifier." in the token stream.  Also
improve a diagnostic a bit.

llvm-svn: 85056