Make improvements

- Improved async signal safety of read() particularly for longjmp()
- Started adding cancel cleanup handlers for locks / etc on Windows
- Make /dev/tty work better particularly for uses like `foo | less`
- Eagerly read console input into a linked list, so poll can signal
- Fix some libc definitional bugs, which configure scripts detected

libc/calls/pause.c

@@ -37,7 +37,9 @@
  *
  * However this has a tinier footprint and better logging.
  *
- * @return -1 w/ errno set to EINTR
+ * @return -1 w/ errno
+ * @raise ECANCELED if this thread was canceled in masked mode
+ * @raise EINTR if interrupted by a signal
  * @cancellationpoint
  * @see sigsuspend()
  * @norestart