Set the FreeBSD clock types

Dispatch passes everything through in nanoseconds, but the default time
on FreeBSD is in milliseconds, resulting in delays taking a million
times longer than expected. This stands out most with `Task.sleep`,
where a 2 second sleep would take hours.

By setting the EVFILT_TIMER filter flag to use nanoseconds, we get the
expected delay.

Also sets up the absolute time flag. The spelling on FreeBSD is
`NOTE_ABSTIME` instead of `NOTE_ABSOLUTE`.

Author: etcwilde

src/event/event_config.h

@@ -118,7 +118,11 @@
 
 // FreeBSD's kevent does not support those
 #	ifndef NOTE_ABSOLUTE
-#	define NOTE_ABSOLUTE 0
+#		ifdef NOTE_ABSTIME
+#			define NOTE_ABSOLUTE NOTE_ABSTIME
+#		else
+#			define NOTE_ABSOLUTE 0
+#		endif
 #	endif
 #	ifndef NOTE_EXITSTATUS
 #	define NOTE_EXITSTATUS 0

src/event/event_kevent.c

@@ -50,6 +50,10 @@ DISPATCH_STATIC_GLOBAL(struct dispatch_muxnote_bucket_s _dispatch_sources[DSL_HA
 #define DISPATCH_NOTE_CLOCK_WALL      NOTE_NSECONDS | NOTE_MACH_CONTINUOUS_TIME
 #define DISPATCH_NOTE_CLOCK_MONOTONIC NOTE_MACHTIME | NOTE_MACH_CONTINUOUS_TIME
 #define DISPATCH_NOTE_CLOCK_UPTIME    NOTE_MACHTIME
+#elif __FreeBSD__
+#define DISPATCH_NOTE_CLOCK_WALL      NOTE_NSECONDS
+#define DISPATCH_NOTE_CLOCK_MONOTONIC NOTE_NSECONDS
+#define DISPATCH_NOTE_CLOCK_UPTIME    NOTE_NSECONDS
 #else
 #define DISPATCH_NOTE_CLOCK_WALL      0
 #define DISPATCH_NOTE_CLOCK_MONOTONIC 0