[analyzer] Bug identification

[analyzer] Bug identification

This patch adds hashes to the plist and html output to be able to identfy bugs
for suppressing false positives or diff results against a baseline. This hash
aims to be resilient for code evolution and is usable to identify bugs in two
different snapshots of the same software. One missing piece however is a
permanent unique identifier of the checker that produces the warning. Once that
issue is resolved, the hashes generated are going to change. Until that point
this feature is marked experimental, but it is suitable for early adoption.

Differential Revision: http://reviews.llvm.org/D10305

Original patch by: Bence Babati!

llvm-svn: 251011