FVWM: popup menus stay on top, please? #906

Hi folks,

is there an option to make sure the F8 popup menu of xtigervncviewer is
shown on top of the program's window itself? Just by accident I discovered
the popup actually "pops under" sometimes, hiding it from the user.

I have set
```
#
# Transient Windows
#
Style	*	DecorateTransient, RaiseTransient, DontLowerTransient, StackTransientParent
Style	*	UseTransientPPosition
```
(inherited from my old fvwm2 config), but these popups are not decorated,
so either they are not transient, or something overrides fvwm. Talking
about fvwm2: I cannot reproduce the problem with fvwm2, usiing the same
config file.


Regards
Harri