[esan|cfrag] Add the struct field offset array in StructInfo

Summary:
Adds the struct field offset array in the struct StructInfo.

Prints struct size and field offset info in the report.

Reviewers: aizatsky

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

Differential Revision: http://reviews.llvm.org/D21191

llvm-svn: 272363