more -Wall warning fixes. -Wall is enabled now.

diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index 915b74d..fe3c647 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -262,7 +262,7 @@
 
 /* It is perfectly ok to pass in a NULL for either width or for
  * height, in which case that value will not be set.  */
-int get_terminal_width_height(int fd, int *width, int *height)
+int get_terminal_width_height(int fd, unsigned *width, unsigned *height)
 {
 	struct winsize win = { 0, 0, 0, 0 };
 	int ret = ioctl(fd, TIOCGWINSZ, &win);