package/x11r7/xlib_libXpm: Add gettext/iconv support

package/x11r7/xlib_libXpm: Add gettext/iconv support

This package uses gettext/iconv when needed

fli4l@fli4lbuild64:~/br5$ output/host/usr/bin/i586-buildroot-linux-uclibc-readelf -a output/target/usr/lib/libXpm.so | grep NEEDED
 0x00000001 (NEEDED)                     Shared library: [libX11.so.6]
 0x00000001 (NEEDED)                     Shared library: [libxcb.so.1]
 0x00000001 (NEEDED)                     Shared library: [libXau.so.6]
 0x00000001 (NEEDED)                     Shared library: [libXdmcp.so.6]
 0x00000001 (NEEDED)                     Shared library: [libdl.so.0]
 0x00000001 (NEEDED)                     Shared library: [libintl.so.8]
 0x00000001 (NEEDED)                     Shared library: [libiconv.so.2]
 0x00000001 (NEEDED)                     Shared library: [libc.so.0]

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>