qt4-webos: add fontconfig, libxext and icu to DEPENDS

* fixes failing do_install:
  tmp-eglibc/work/tuna-webos-linux-gnueabi/qt4-webos-4.8.2.03-1.02-r33.1/git/src/corelib/tools/qlocale_icu.cpp:46:30:
    fatal error: unicode/uversion.h: No such file or directory
  make[1]: *** No rule to make target
    `tmp-eglibc/sysroots/tuna/usr/include/fontconfig/fontconfig.h',
    needed by `.obj/release-shared/qgl.o'.  Stop.
  make[1]: *** No rule to make target
    `tmp-eglibc/sysroots/tuna/usr/include/X11/extensions/shape.h',
    needed by `.obj/release-shared/qgl.o'.  Stop.

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>