More scanf cleanup.

Merge CT_CCL and CT_STRING handling before we add %m.

Also fix an accidental scanf/wscanf difference.

Add currently-disabled tests for questionable behavior noticed during
code review that isn't a regression, but should be fixed later.

Bug: http://b/68672236
Bug: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=202240
Test: ran tests
Change-Id: I3eec9b7dfce84f63c68426406224822c52551d64