allow brk > 2gb.

Notes:
Fri Apr 29 15:36:33 EDT 2011 geoff
    done differently.


Reference: /n/sources/patch/applied/apemalloc
Date: Thu Apr 28 17:24:41 CES 2011
Signed-off-by: quanstro@quanstro.net
Reviewed-by: geoff

--- /sys/src/ape/lib/ap/plan9/malloc.c	Thu Apr 28 17:24:36 2011
+++ /sys/src/ape/lib/ap/plan9/malloc.c	Thu Apr 28 17:24:35 2011
@@ -64,7 +64,7 @@
 	if(pow < CUTOFF) {
 		n = (CUTOFF-pow)+2;
 		bp = sbrk(size*n);
-		if((int)bp < 0)
+		if(bp == (Bucket*)-1)
 			return nil;
 
 		next = (uint)bp+size;
@@ -80,7 +80,7 @@
 	}
 	else {
 		bp = sbrk(size);
-		if((int)bp < 0)
+		if(bp == (Bucket*)-1)
 			return nil;
 	}