CVS domivogt: Fix gcc -O3 warnings.

[cvs]

CVSROOT:        /home/cvs/fvwm
Module name:    fvwm
Changes by:     domivogt        14/09/15 13:04:19

Modified files:
        fvwm           : Tag: branch-2_6 frame.c 
        .              : Tag: branch-2_6 ChangeLog 

Log message:
Fix gcc -O3 warnings.