Heads up on some changes to LLVM's IPO model around ODR functions

Hi all,

This is an FYI for a change I'm about to check in:
http://reviews.llvm.org/D18634. D18634 fixes soundness issues around
LLVM's IPO model by disabling some optimizations that we previously
thought were valid (but aren't) for *_odr linkage types. You can find
all of the gory details on the Phabricator review.

PS: I'm not on cfe-dev, so I won't see replies sent solely to cfe-dev

-- Sanjoy