more documentation

CHANGES

@@ -6,6 +6,12 @@
     scanned something
   io_sendfile and iob_send should return -1 to -3 just like io_trywrite
   make io_waituntil actually take an "until", not a "how long"
+  turns out that BSD kqueue is actually Free/OpenBSD kqueue -- NetBSD
+    doesn't have it.  That means I'll need some adaptive two-threads-
+    running-poll approach to get C10k type scalability on NetBSD :-(
+  turns out that BSD sendfile is actually FreeBSD sendfile -- neither
+    OpenBSD nor NetBSD have it (as of 3.4 and 1.6.1).  That means I'll
+    need to try using mmap on OpenBSD and NetBSD to get zero-copy TCP.
 
 0.16:
   add buffer_fromsa (make buffer from stralloc)