Rewrite page(2) references to page(3).

Add description of new libmach.

man/man3/keyboard.3

@@ -23,14 +23,14 @@ void			closekeyboard(Keyboard *kc)
 .SH DESCRIPTION
 These functions access and control a keyboard interface
 for character-at-a-time I/O in a multi-threaded environment, usually in combination with
-.IR mouse (2).
+.IR mouse (3).
 They use the message-passing
 .B Channel
 interface in the threads library
 (see
-.IR thread (2));
+.IR thread (3));
 programs that wish a more event-driven, single-threaded approach should use
-.IR event (2).
+.IR event (3).
 .PP
 .I Initkeyboard
 opens a connection to the keyboard and returns a
@@ -94,10 +94,10 @@ structure.
 .SH SOURCE
 .B /sys/src/libdraw
 .SH SEE ALSO
-.IR graphics (2),
-.IR draw (2),
-.IR event (2),
-.IR thread (2).
+.IR graphics (3),
+.IR draw (3),
+.IR event (3),
+.IR thread (3).
 .SH BUGS
 Because the interface delivers complete runes,
 there is no way to report lesser actions such as