[PATCH] [SCEV] Improve Scalar Evolution's use of no {un, }signed wrap flags

[hfinkel at anl.gov]

Please post patches will full context, see http://llvm.org/docs/Phabricator.html#requesting-a-review-via-the-web-interface for more information.

(also, adding Andy)

http://reviews.llvm.org/D6002