Ooopsify write-string/partial.

doc/scsh-manual/syscalls.tex

@@ -936,6 +936,9 @@ Returns two ports, the read and write end-points of a {\Unix} pipe.
     Non-blocking I/O is only available on file descriptors and unbuffered
     ports. Doing non-blocking I/O to a buffered port is not well-defined,
     and is an error (the problem is the subsequent flush operation).
+    
+    \oops{\ex{write-string/partial} is currently not implemented.
+      Consider using threads to achive the same functionality.}
 \end{defundescx}
 
 \subsection{Buffered I/O}