Makefile.am: add pageant.1 to the man pages collection.

It wasn't built or installed by the normal make process. Oops.

Recipe

@@ -186,7 +186,7 @@ install-strip:
 !begin am
 if HAVE_GTK
 man1_MANS = doc/plink.1 doc/pscp.1 doc/psftp.1 doc/puttygen.1 \
-	    doc/pterm.1 doc/putty.1 doc/puttytel.1
+	    doc/pageant.1 doc/pterm.1 doc/putty.1 doc/puttytel.1
 else
 man1_MANS = doc/plink.1 doc/pscp.1 doc/psftp.1 doc/puttygen.1
 endif