Fixed a bug in noit_skiplist_remove_compare

noit_skiplist_remove_compare was not correctly finding elements to remove;
corrected it so that it correctly finds and removes elements.
Fixed a bug with processes crashing in noit_watchdog.c

If the main process spawned off a new process and that process crashed,
the noit watchdog emancipate code was not handling it correctly and could
lead to processes being put to sleep and never woken up. Added code to
detect this case and handle it.
Fixed some bug in the external check

The external check was occasionally crashing, getting hung up, etc. Fixed
these bugs.