swift234

Fix IDE crashers 027, 066, and 068.

Expand the "skip" functions in the parser to be more careful about
not skipping passed a #endif or a code completion token, since they
are synchronization points for the parser.

The fix was to change Parser::delayParseFromBeginningToHere to use
a manual loop instead of skipUntil (which can stop early for non-EOF
tokens).