screen: enable support for 256 colors

Support for 256 colors is enabled in xterm and ncurses, but it was
forgotten for screen.

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/screen/screen.mk

@@ -11,6 +11,7 @@ SCREEN_LICENSE_FILES = COPYING
 SCREEN_DEPENDENCIES = ncurses
 SCREEN_AUTORECONF = YES
 SCREEN_CONF_ENV = CFLAGS="$(TARGET_CFLAGS)"
+SCREEN_CONF_OPTS = --enable-colors256
 SCREEN_INSTALL_TARGET_OPTS = DESTDIR=$(TARGET_DIR) SCREEN=screen install_bin
 
 define SCREEN_INSTALL_SCREENRC