[esan] Add calls from the ctor/dtor to the runtime library

Summary:
Adds createEsanInitToolGV for creating a tool-specific variable passed
to the runtime library.

Adds dtor "esan.module_dtor" and inserts calls from the dtor to
"__esan_exit" in the runtime library.

Updates the EfficiencySanitizer test.

Patch by Qin Zhao.

Reviewers: aizatsky

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

Differential Revision: http://reviews.llvm.org/D20488

llvm-svn: 270627