[Analyzer][StreamChecker] Added support for 'fread' and 'fwrite'.

Summary:
Stream functions `fread` and `fwrite` are evaluated
and preconditions checked.
A new bug type is added for a (non fatal) warning if `fread`
is called in EOF state.

Reviewers: Szelethus, NoQ, dcoughlin, baloghadamsoftware, martong, xazax.hun

Reviewed By: Szelethus

Subscribers: rnkovacs, xazax.hun, baloghadamsoftware, szepet, a.sidorin, mikhail.ramalho, Szelethus, donat.nagy, dkrupp, gamesh411, Charusso, martong, ASDenysPetrov, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D80015