fix test.py
Added dot (".") to find so that it runs on OS X.
Wiped out STATIC_LIBRARY_PATHS variable for building on OS X.  (Maybe temporary.)
Added signal.h to errors.hpp.
Made spawner_t::exec_worker put prctl on separate line from guarantee.
Commented out mcheck.h and added -Wno-format-nonliteral.
Renamed uuid_t to uuid_u.
Made linux_message_hub_t use spinlock_t instead of pthread_spinlock_t.
Made spinlock_t use a pthread_mutex_t when __APPLE__.
Made linux_thread_pool_t use spinlock_t.
Commented out <linux/fs.h>, which seems unused.
Added timer_itimer_provider_t, currently not actually hooked up properly, to skip timerfd and timer_signal_provider_t compilation errors in OS X.
Made microtime_t be printed out as a long long in activity_logger.cc.
Removed unused uncompiling-on-OS-X functions get_available_ram and get_total_ram.
Fixed compilation problems in timer_itimer_provider.cc.
Commented out prctl function and include.
Removed unused variable res in linux_message_hub_t destructor.
Removed some attempted uses of the private lock() and unlock() members of spinlock_t.
Made str_gethostname use sysconf(_SC_HOST_NAME_MAX) on OS X.
Changed format specifier for pet_watchdog.