[esan|cfrag] Add struct array access report

Summary:
Adds struct array access counter report.

Updates test struct-simple.cpp.

Reviewers: aizatsky

Subscribers: vitalybuka, zhaoqin, kcc, eugenis, bruening, llvm-commits, kubabrecka

Differential Revision: http://reviews.llvm.org/D21595

llvm-svn: 274421