Document mouse buttons.
 [rsc] --rw-rw-r-- M 323293 presotto sys 1732 Nov  4 08:15 sys/man/3/kbmap
	/n/sourcesdump/2005/1104/plan9/sys/man/3/kbmap:46,58 - 
	/n/sourcesdump/2005/1105/plan9/sys/man/3/kbmap:46,61
	  .IR utf (6)),
	  or as 
	  .BI ^ X
	- to represent a control character or as
	- .BI M n
	- to represent a mouse button.
	+ to represent a control character.
	  .PP
	+ The Unicode character can also be
	+ .BI M n
	+ to represent mouse button
	+ .IR n .
	  The map
	  .B /sys/lib/kbmap/mouse-fn
	- maps the F1, F2, and F3 keys to the three mouse buttons.
	+ maps the F1 through F5 keys to the three mouse buttons and the two
	+ scroll wheel buttons.
	  Similarly, 
	  .B mouse-csa
	  maps the left Control, Start, and Alt keys to the three mouse buttons.