Instead of creating a GdkX11Cursor, create GdkCursors. Cache the XCursor
in a hash table instead.
Also, make use of the new fallback mechanism for fallback code: Make
sure to provide cursors for the names that are guaranteed to exist, but
do not do bad attempts at displaying texture surfaces.
Black/White/transparent is not a replacement for those.
Make sure that the tests don't access the host's session bus or
installed gsettings schemas.
Also disable tests for some classes that leak a connection to the
session bus.
https://bugzilla.gnome.org/show_bug.cgi?id=711715
