Don't use super to get the parent do_* methods of gtk widget

With some version of GTK, using super call to get the do_* function doesn't
work.  It seems it returns a meta function that will call back the do_* of the
instance. So this leads to an infinite loop.

issue4016
review5421002
Block changed method when setting value in display of selection widget

When displaying record value, selection should not call focus_out.

issue3698
review11351002
Use PopdownMixin for autocompletion on Char

issue3985
review6381002