Send up-events for scroll wheel.
 [rsc] --rw-rw-r-- M 1118886 rsc sys 4197 Jan 23 20:16 sys/src/cmd/vnc/wsys.c
	/n/sourcesdump/2006/0123/plan9/sys/src/cmd/vnc/wsys.c:147,154 - 
	/n/sourcesdump/2006/0124/plan9/sys/src/cmd/vnc/wsys.c:147,160
	  				m.xy.y = atoi(start+1+12);
	  				m.buttons = atoi(start+1+2*12) & 0x1F;
	  				m.xy = subpt(m.xy, screen->r.min);
	- 				if(ptinrect(m.xy, Rpt(ZP, v->dim)))
	+ 				if(ptinrect(m.xy, Rpt(ZP, v->dim))){
	  					mouseevent(v, m);
	+ 					/* send wheel button *release* */ 
	+ 					if ((m.buttons & 0x7) != m.buttons) {
	+ 						m.buttons &= 0x7;
	+ 						mouseevent(v, m);
	+ 					}
	+ 				}
	  			} else
	  				eresized();