Use sigprocmask to opt out of signals

This basically sets the procmask before lighting up apache, which in
turn will bind up it's own signal handlers, but once it's running we
once again block all calls to SIGWINCH.

The impact of this is that long term if you do a ton of resizing the
signals will backup until you hit undefined behaviour eventually.
Whitespace
Only block signals if the platform supports it
Merge pull request #2 from lox/features/defer_signals

Prevent SIGWINCH from terminating apache