swift234

Set and check invalid bits on declarations more regularly.

Fixes various crashes and cascading failures, such as
<rdar://problem/14705781>, and gets us closer to having sane "invalid"
bit settings on declarations <rdar://problem/10157547>.

Also, clean up after ourselves better when we fail to pre-check or
type-check an expression. Fixes <rdar://problem/14540304>.



Swift SVN r7292