[gtkada] Slowness on Linux: solved

[manuel.op.de.coul at eon-benelux.com]

Thanks to the help of Charles Darcy and Prebel Randhol the problem
was solved by changing the GNAT runtime from 'rts-fsu' to 'rts-native'.
Now the widgets are drawn very fast.

So there must be a problem with the combination of FSU threads with GTK,
GNAT 3.13p and Linux.

Cheers,

Manuel