xterm: depend on libXinerama if appropriate

xterm: depend on libXinerama if appropriate

xterm may depends on libXinerama.so:

$ arm-linux-readelf -d ./usr/bin/xterm | grep NEEDED
 0x00000001 (NEEDED)                     Shared library: [libXft.so.2]
 0x00000001 (NEEDED)                     Shared library: [libfontconfig.so.1]
 0x00000001 (NEEDED)                     Shared library: [libXmu.so.6]
 0x00000001 (NEEDED)                     Shared library: [libXaw.so.7]
 0x00000001 (NEEDED)                     Shared library: [libXt.so.6]
 0x00000001 (NEEDED)                     Shared library: [libX11.so.6]
 0x00000001 (NEEDED)                     Shared library: [libXinerama.so.1]
 0x00000001 (NEEDED)                     Shared library: [libXpm.so.4]
 0x00000001 (NEEDED)                     Shared library: [libICE.so.6]
 0x00000001 (NEEDED)                     Shared library: [libncursesw.so.6]
 0x00000001 (NEEDED)                     Shared library: [libc.so.6]

However, build order with libXinerama is not defined.

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