[path] StdPath:move_handle() experimental shear and perspective

StdPath:move_handle() is not fully reversible as it has to be
according to Dia's standards. Alternatively it might be possible
to return a respective change to make undo work. But also there
should be some more handle movement restrictions to not completely
deform (and loose) the path ...
Bug 709017 [warningectomy] array subscript is above array bounds

Get rid of the temporary array for font name, loose the limitation
of maximum font name length and spare a string copy.