Implement an additional fix for infinite recursion of deleted special

member functions by making sure that they're on the record before
checking for deletion.

Also make sure source locations are valid to avoid crashes.

Unfortunately, the declare-all-implicit-members approach is still
required in order to ensure that dependency loops do not result in
incorrectly deleting functions (since they are to be deleted at the
declaration point per the standard).

Fixes PR9917

llvm-svn: 131520