[esan:cfrag] Add option -esan-aux-field-info

Summary:
Adds option -esan-aux-field-info to control generating binary with
auxiliary struct field information.

Extracts code for creating auxiliary information from
createCacheFragInfoGV into createCacheFragAuxGV.

Adds test struct_field_small.ll for -esan-aux-field-info test.

Reviewers: aizatsky

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

Differential Revision: http://reviews.llvm.org/D22019

llvm-svn: 274726