Bug 1496503 - Move MOZ_CrashOOL to Assertions.h. r=froydnj

Ideally, we'd want the function to stay in Assertions.cpp, but that's
only part of MFBT proper, and that doesn't have access to WalkTheStack
like MOZ_CRASH has from being in Assertion.h, when included from Gecko
code. Moving WalkTheStack to mozglue, putting it close together with
MozStackWalk would be prefered, but that causes problems linking MFBT
tests (which don't have access to mozglue), and other things.

Overall, this was too deep a rabbit hole, and moving MOZ_CrashOOL to
Assertions.h is much simpler. Since it's essentially the same as
MOZ_CRASH, except it allows non-literal strings, we can make it inlined,
and leave it to the compiler to drop the filename argument when it's not
used.

Differential Revision: https://phabricator.services.mozilla.com/D11718

--HG--
extra : moz-landing-system : lando