recipes-graphics/lxdm: autotools and config updates

lxdm_git.bb: Upstream changes required autotools and gettext (intl) updates;
the package autogen script doesn't create the makefile in po, but autotools
by itself is missing the input file (thus, the configure_prepend). There
were also missing depends (from upstream docs and configure checks) and
some configure options were added to ensure the desired X/gtk2 config and
enable (optional) auto-login.

Signed-off-by: Stephen Arnold <stephen.arnold42@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>