also remove _xinc from 9/pc.  it wasn't used after all

Reference: /n/atom/patch/applied/noinc9pc
Date: Fri Jun  6 19:12:02 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/9/pc/l.s	Fri Jun  6 19:11:43 2014
+++ /sys/src/9/pc/l.s	Fri Jun  6 19:11:43 2014
@@ -867,25 +867,6 @@
 	XCHGL	AX, (BX)			/* lock->key */
 	RET
 
-TEXT _xinc(SB), 1, $0				/* void _xinc(long*); */
-	MOVL	l+0(FP), AX
-	LOCK;	INCL 0(AX)
-	RET
-
-TEXT _xdec(SB), 1, $0				/* long _xdec(long*); */
-	MOVL	l+0(FP), BX
-	XORL	AX, AX
-	LOCK;	DECL 0(BX)
-	JLT	_xdeclt
-	JGT	_xdecgt
-	RET
-_xdecgt:
-	INCL	AX
-	RET
-_xdeclt:
-	DECL	AX
-	RET
-
 TEXT mb386(SB), 1, $0
 	POPL	AX				/* return PC */
 	PUSHFL
--- /sys/src/9/pc/sdodin.c	Fri Jun  6 19:11:43 2014
+++ /sys/src/9/pc/sdodin.c	Fri Jun  6 19:11:43 2014
@@ -881,9 +881,9 @@
 	n = cmd | Ditor | i*Dsatareg | m*Dphyno | i*Dcslot;
 //	print("cqwp\t%.8ux : n %ux : d%d; \n", c->cq[0], n, i);
 	/*
-	 * xinc doesn't return the previous value and i can't
+	 * ainc doesn't return the previous value and i can't
 	 * figure out how to do this without a lock
-	 *	s = _xinc(&c->dqwp);
+	 *	s = ainc(&c->dqwp);
 	 */
 	d->cmd->cflag = Active;
 	ilock(c);
--- /sys/src/9/pc/ethervt6105m.c	Fri Jun  6 19:11:43 2014
+++ /sys/src/9/pc/ethervt6105m.c	Fri Jun  6 19:11:43 2014
@@ -594,7 +594,7 @@
 	if((bp = vt6105Mrbpool) != nil){
 		vt6105Mrbpool = bp->next;
 		bp->next = nil;
-//		_xinc(&bp->ref);	/* prevent bp from being freed */
+//		ainc(&bp->ref);	/* prevent bp from being freed */
 	}
 	iunlock(&vt6105Mrblock);