src/misc: translate_app_exec_to_command_line() don't append space at end

urxvt cannot handle spaces at the end, see
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=687615
autogen.sh: change to use autoreconf et al

Using an automake version check in autogen.sh does not make much sense.
This autogen.sh should be the same across most LXDE packages, so let's
use it here.