Use the standard expression for the availability statement for alarm().
diff --git a/Doc/lib/libsignal.tex b/Doc/lib/libsignal.tex
index f77f0a8..e3aa171 100644
--- a/Doc/lib/libsignal.tex
+++ b/Doc/lib/libsignal.tex
@@ -103,8 +103,9 @@
If \var{time} is zero, no alarm id scheduled, and any scheduled
alarm is canceled. The return value is the number of seconds
remaining before a previously scheduled alarm. If the return value
- is zero, no alarm is currently scheduled. Not on Windows. (See the
- \UNIX{} man page \manpage{alarm}{2}.)
+ is zero, no alarm is currently scheduled. (See the \UNIX{} man page
+ \manpage{alarm}{2}.)
+ Availability: \UNIX.
\end{funcdesc}
\begin{funcdesc}{getsignal}{signalnum}