libmach, cmd/8l: fix Plan 9 warnings

warning: src/libmach/sym.c:1861 non-interruptable temporary
warning: src/cmd/8l/../ld/pcln.c:29 set and not used: p

R=golang-dev, gobot, rsc
CC=golang-dev
https://golang.org/cl/40500043

src/cmd/ld/pcln.c

@@ -26,7 +26,7 @@ addvarint(Pcdata *d, uint32 val)
 	p = d->p + d->n;
 	for(v = val; v >= 0x80; v >>= 7)
 		*p++ = v | 0x80;
-	*p++ = v;
+	*p = v;
 	d->n += n;
 }
 

src/libmach/sym.c

@@ -1858,7 +1858,8 @@ havefile:
 		fp = pcline + pcswal(*(uint32*)(func+FuncPCFile));
 		lp = pcline + pcswal(*(uint32*)(func+FuncPCLine));
 		fval = lval = -1;
-		fpc = lpc = entry;
+		lpc = entry;
+		fpc = lpc;
 		fstartpc = fpc;
 		while(step(&fp, &fpc, &fval, fpc==entry)) {
 			if(fval == fno && fstartpc < fpc) {