This is a free-form tab that can contain information about the
system environment. To see it, set GtkAboutDialog::system-information
to a non-NULL value.
https://bugzilla.gnome.org/show_bug.cgi?id=776604
This reverts commit 6af5033386.
Scrolled window behavior of propagating child natural sizes
has now been made optional, so there is no need to work around
this by setting a hard coded maximum content height anymore.
Making a container focusable is rarely the right thing to do.
It typically breaks the focus chain, and makes the container
contents unfocusable, as was the case here.
This subdirectory gets in the way when integrating the inspector
build more fully with GTK+, and does not really add anything.
Just move everything one level up.
