swift234

rename AddVarsToScope to CollectVarsAndAddToScope and move it
down next to case statement parsing logic since it is specific to
it.  It looks like we can't fully eliminate this right now, because
patterns in case statements are parsed generally as expr patterns
and sema'd into something more useful later, too late for setting
variables in scopes.  The parsing logic could be improved here, but
I'm not going to work on this. 

As a driveby, improve error recovery when type checking of case
statement patterns fails by marking the decls inside of them as
invalid.


Swift SVN r13712