Make icon reading a bit more robust by requiring the actual parameter (even
if it is allowed to be 0) and splitting it up into smaller methods.
This should help #215 pekwm crashes when opening new Opera 10
Two new atoms were introduces to keep track of the ordering within Frames
_PEKWM_FRAME_ORDER and which client is the active one _PEKWM_FRAME_ACTIVE.
Restart tests on my PC seems to be working ok.