configure: silence pkg-config's check for curses

Signed-off-by: NVadim Evard <v.e.evard@gmail.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

configure

@@ -2039,7 +2039,7 @@ fi
 if test "$mingw32" = "yes" ; then
     curses_list="-lpdcurses"
 else
-    curses_list="-lncurses:-lcurses:$($pkg_config --libs ncurses)"
+    curses_list="-lncurses:-lcurses:$($pkg_config --libs ncurses 2>/dev/null)"
 fi
 
 if test "$curses" != "no" ; then