venti: fix venti graph on 64-bit

A pixel is 32 bits wide in RGBA, regardless of system's word size.

Change-Id: Iea36a8dafdec9ce8d593f944ef5ed1ea08e11d25
Reviewed-on: https://plan9port-review.googlesource.com/2980
Reviewed-by: David du Colombier <0intro@gmail.com>

CONTRIBUTORS

diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 0b9a541..871c757 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -35,6 +35,7 @@
 Martin Neubauer <m.ne@gmx.net>
 Mathieu Lonjaret <lejatorn@gmail.com>
 Mathieu Lonjaret <mathieu.lonjaret@gmail.com>
+Michael Stroucken <mxs@cmu.edu>
 Michael Teichgräber <mt4swm@googlemail.com>
 Michael Teichgräber <mt@ib.wmipf.de>
 Nathaniel W Filardo <nwf@cs.jhu.edu> <nwfilardo@gmail.com>

src/cmd/venti/srv/png.c

diff --git a/src/cmd/venti/srv/png.c b/src/cmd/venti/srv/png.c
index ca45641..8805ada 100644
--- a/src/cmd/venti/srv/png.c
+++ b/src/cmd/venti/srv/png.c
@@ -212,7 +212,7 @@
 	/* image data */
 	zr.dx = Dx(m->r);
 	zr.dy = Dy(m->r);
-	zr.width = rgb->width * sizeof(ulong);
+	zr.width = rgb->width * sizeof(u32int);
 	zr.data = rgb->data->bdata;
 	zr.x = 0;
 	zr.y = 0;