Add ability for handlers to 'fatally' fail, so they won't attempt to
reinstall themselves later.

Also fix an issue with the INT_LOG macro not doing the right thing when
only the lager_throttle_backend was installed.

This fixes a bug where messages were incorrectly discarded if the new
handler is using log levels that are different from those in use by handlers
that were set up at start-of-day.

This also removes the dependency on the syntax_tools and compiler
applications, which interfered with lager's startup/shutdown order.

This is just silly busy-work since they're library applications, but
whatever.