When a GL context group is destroyed, all multi-group shared
resources associated with the group should be cleaned up.
Otherwise we could get a double deletion in the resource's
destructor, because it still retained a pointer to the
deleted group.
The missing cleanup resulted in a crash when the global
static qt_gl_functions_resource was destroyed, first seen
in the tst_examples autotest in qtdeclarative. It possibly
didn't manifest before because it's event loop-dependent
(the contexts are deleted via deleteLater()).
Change-Id: I6b1e0bfdfbbb2bff8e795f545e680fcdfa094768
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>
202127f860