Fixed "mcs failing to load plugins"-issue

[Benedikt Meurer]

Hello,

I think I fixed the problem some people had with mcs failing to load plugins.
The problem was, that for some reason, they were using a bogus version of
gmodule, which does not seem to include -Wl,--export-dynamic, and that
prevents the run time linker from resolving the dynamic symbols.

-export-dynamic is now explicitly set by libxfce4mcs and also for the
files in xfce-mcs-{manager,plugins}.

I hope this will work :-)

regards,
Benedikt

-- 
Those who do not understand Unix are condemned to reinvent it, poorly.
    -- Henry Spencer