[Analyzer][StreamChecker] Added evaluation of fseek.

Summary:
Function `fseek` is now evaluated with setting error return value
and error flags.

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

Reviewed By: Szelethus

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75851