fix a few trivial bits in qmalloc.

Reference: /n/patches.lsub.org/patch/qmallocnits
Date: Sun Oct 28 17:38:59 CET 2012
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/port/qmalloc.c	Wed Mar 28 17:42:23 2012
+++ /sys/src/nix/port/qmalloc.c	Sun Oct 28 16:42:31 2012
@@ -252,10 +252,8 @@
 	Header *p, *q;
 	uint nunits, n;
 
-///* FIXME: (ignore for now)
 	if(nbytes == 0)
 		return nil;
-//*/
 
 	qstats[QSmalloc]++;
 	nunits = NUNITS(nbytes);
@@ -323,7 +321,7 @@
 
 	p = (Header*)ap - 1;
 	if((nunits = p->s.size) == 0 || p->s.next != &checkval)
-		panic("malloc: corrupt allocation arena\n");
+		panic("malloc: corrupt allocation arena");
 	if(tailptr != nil && p+nunits == tailptr) {
 		/* block before tail */
 		tailptr = p;
@@ -374,7 +372,7 @@
 
 	p = (Header*)ap - 1;
 	if((nunits = p->s.size) == 0 || p->s.next != &checkval)
-		panic("malloc: corrupt allocation arena\n");
+		panic("malloc: corrupt allocation arena");
 
 	return (nunits-1) * sizeof(Header);
 }
@@ -581,7 +579,7 @@
 
 	p = (Header*)ap - 1;
 	if((ounits = p->s.size) == 0 || p->s.next != &checkval)
-		panic("realloc: corrupt allocation arena\n");
+		panic("realloc: corrupt allocation arena");
 
 	if((nunits = NUNITS(size)) == ounits)
 		return ap;