fix masking of qid.path

Reference: /n/atom/patch/applied/nixpathmask
Date: Sat Aug 15 23:23:04 CES 2015
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/port/sysfile.c	Sat Aug 15 23:22:47 2015
+++ /sys/src/nix/port/sysfile.c	Sat Aug 15 23:22:49 2015
@@ -1380,7 +1380,7 @@
 	p += 28;
 	strncpy((char*)p, d->gid, 28);
 	p += 28;
-	q = d->qid.path & ~DMDIR;	/* make sure doesn't accidentally look like directory */
+	q = d->qid.path & ~(uvlong)DMDIR;	/* make sure doesn't accidentally look like directory */
 	if(d->qid.type & QTDIR)	/* this is the real test of a new directory */
 		q |= DMDIR;
 	PBIT32(p, q);