[analyzer] Pass the correct loc Expr from VisitIncDecOp to evalStore

Summary: The LocationE parameter of evalStore is documented as "The location expression that is stored to". When storing from an increment / decrement operator this was not satisfied. In user code this causes an inconsistency between the SVal and Stmt parameters of checkLocation.

Reviewers: NoQ, dcoughlin, george.karpenkov

Reviewed By: NoQ

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

Differential Revision: https://reviews.llvm.org/D55701

llvm-svn: 350528