CVS griph: only convert the _NET_WM_ICON property to long before changing it

[FVWM CVS]

CVSROOT:        /home/cvs/fvwm
Module name:    fvwm
Changes by:     griph   09/08/28 06:24:28

Modified files:
        .              : ChangeLog NEWS 
        fvwm           : ewmh.c 

Log message:
only convert the _NET_WM_ICON property to long before changing it