[esan] EfficiencySanitizer driver flags

Summary:
Adds a framework to enable the instrumentation pass for the new
EfficiencySanitizer ("esan") family of tools.  Adds a flag for esan's
cache fragmentation tool via -fsanitize=efficiency-cache-frag.
Adds appropriate tests for the new flag.

Reviewers: eugenis, vitalybuka, aizatsky, filcab

Subscribers: filcab, kubabrecka, llvm-commits, zhaoqin, kcc

Differential Revision: http://reviews.llvm.org/D19169

llvm-svn: 267059