[esan|cfrag] Add struct info registration

Summary:
Adds StructInfo to CacheFragInfo to match the LLVM's EfficiencySanitizer
structs.

Uses StructHashMap to keep track of the struct info used by the app.

Adds registerStructInfo/unregisterStructInfo to add/remove struct infos
to/from StructHashMap.

updates test struct-simple.cpp with more C structs.

Reviewers: aizatsky, filcab

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

Differential Revision: http://reviews.llvm.org/D20590

llvm-svn: 271564