The technical etc. move modes using a shaped window ("avoid server grab"
mode) only properly shaped the shape window of the first group member.
Broken since 0c16916258 - v1.0.12.
This commit changed the mode of operation from one shape window in total
to one per group member, i.e. shapes should no longer be combined.
..and drop useless fl variable in _MoveResizeMoveResume().