[Checkers] Added support for freopen to StreamChecker.

Summary: Extend StreamChecker with a new evaluation function for API call 'freopen'.

Reviewers: NoQ, baloghadamsoftware, Szelethus, martong

Reviewed By: baloghadamsoftware, martong

Subscribers: martong, rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D69948