[Analyzer] Iterator Checker - Part 7: Support for push and pop operations

This patch adds support for the following operations in the iterator checkers: push_back, push_front, emplace_back, emplace_front, pop_back and pop_front. This affects iterator range checks (range is extended after push and emplace and reduced after pop operations) and invalidation checks (according to the standard).

Differential Revision: https://reviews.llvm.org/D32902

llvm-svn: 341793