libbb: factor out code which queries screen width

function                                             old     new   delta
get_terminal_width                                     -      17     +17
stty_main                                           1196    1197      +1
pstree_main                                          321     319      -2
ls_main                                              735     731      -4
watch_main                                           232     225      -7
bb_progress_update                                   714     706      -8
ps_main                                              555     543     -12
run_applet_and_exit                                  708     695     -13
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/6 up/down: 18/-46)            Total: -28 byte

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/progress.c b/libbb/progress.c
index 372feb0..6154dca 100644
--- a/libbb/progress.c
+++ b/libbb/progress.c
@@ -45,13 +45,6 @@
 	STALLTIME = 5
 };
 
-static unsigned int get_tty2_width(void)
-{
-	unsigned width;
-	get_terminal_width_height(2, &width, NULL);
-	return width;
-}
-
 void FAST_FUNC bb_progress_init(bb_progress_t *p, const char *curfile)
 {
 #if ENABLE_UNICODE_SUPPORT
@@ -148,7 +141,7 @@
 		unsigned ratio = 100 * beg_and_transferred / totalsize;
 		fprintf(stderr, "%4u%%", ratio);
 
-		barlength = get_tty2_width() - 49;
+		barlength = get_terminal_width(2) - 49;
 		if (barlength > 0) {
 			/* god bless gcc for variable arrays :) */
 			char buf[barlength + 1];