Set X11 related options for all loaded configs

load_config_file_x11 is called only for the main config, but this goes
against the behaviour for $include for most options. Calling it at the
end of load_config_file will make $include semantics also apply to those
options (such as colorN).
Calculate text width for single character strings

Both get_string_width_special and calc_text_with already have an early
return for output_methods other than TO_X. In the case of TO_X even
for single character strings the width needs to be calculated for
specials, as otherwise $alignr for single characters is wrong.