Fix some uses of uninitialised variables.
Correct for compiler skew between hogun and ise.
Fix some stupid mistakes in the support for old-format call graphs.
Unbreak the no-static-analysis build.
Add a couple more timeout checks.
When we're building the ImportRegister set, we only need to keep
definedness information for the consistent advance frontier.  Clear
out the rest of it.  This reduces memory consumption for that phase
by about a factor of ten, and is also much faster because it means
that the RB trees are much shallower.
Rewrite dead code elimination to be a bit less barking mad.