crop: fix 64-bit

R=rsc
http://codereview.appspot.com/4438088

src/cmd/draw/crop.c

diff --git a/src/cmd/draw/crop.c b/src/cmd/draw/crop.c
index 6ec03b7..10a08f7 100644
--- a/src/cmd/draw/crop.c
+++ b/src/cmd/draw/crop.c
@@ -35,12 +35,12 @@
 }
 
 Rectangle
-crop(Memimage *m, ulong c)
+crop(Memimage *m, uint32 c)
 {
 	Memimage *n;
 	int x, y, bpl, wpl;
 	int left, right, top, bottom;
-	ulong *buf;
+	uint32 *buf;
 
 	left = m->r.max.x;
 	right = m->r.min.x;
@@ -90,7 +90,7 @@
 	Point t;
 	Memimage *m, *new;
 	char *file;
-	ulong bg, cropval;
+	uint32 bg, cropval;
 	long dw;
 
 	memimageinit();