Added a helper function to co_dcli? that executes the first available flavour (wb_qt/wb_gtk/wb_motif) given a base executable (wb).

QT: Changed xtt_multiview to use a tagged union and std::vector instead 7 statically allocated fixed-size arrays.

QT: Fixed ge_curve: the growcurve_main_widget did not respect the size of the other widgets, and thus covered the whole window.

This reverts commit 0af41972fd01ac5d5e7d10de1e2b5872121b99ff.