simplify parse_config using assignment; inspired by a very old diff from
Tiago Cunha.
move some init up and shed some blank lines
Move conf_init/clear into main - no behaviour change; from Tiago Cunha.
The EWMH spec states that if the cardinal returned is 0xFFFFFFFF (-1)
then the window should appear on all desktops, which in our case is
assigned to group 0.  Found to fix stalonetray due to the non-ewmh aware
range checking in group_movetogroup(); from Thomas Adam.
Check ignore windowname for truncation and provide user feedback during
config parse; based on a discussion with Tiago Cunha.