-/* Wait for file descriptor FD to be available, timing out after
- MAXTIME seconds. "Available" means readable if writep is 0,
- writeable otherwise.
+/* Wait for file descriptor FD to be readable or writable or both,
+ timing out after MAXTIME seconds. Returns 1 if FD is available, 0
+ for timeout and -1 for error. The argument WHAT can be a
+ combination of WAIT_READ and WAIT_WRITE.