swift234

Fix <rdar://problem/20985280> QoI: improve diagnostic on improper pattern match on type

Where before we would diagnose something like "catch MyType {" with two errors (one of
which complaining about a ~= the user didn't write) and two notes, we now produce:

 error: 'is' keyword required to pattern match against type name

with a fixit hint to insert the 'is'.



Swift SVN r28761