[Analyzer] Iterator Checkers - Make range errors and invalidated access fatal

Range errors (dereferencing or incrementing the past-the-end iterator or
decrementing the iterator of the first element of the range) and access of
invalidated iterators lead to undefined behavior. There is no point to
continue the analysis after such an error on the same execution path, but
terminate it by a sink node (fatal error). This also improves the
performance and helps avoiding double reports (e.g. in case of nested
iterators).

Differential Revision: https://reviews.llvm.org/D62893

llvm-svn: 370314