Now GtkWrapBox has "horizontal-spreading" and "vertical-spreading" options,
before GtkWrapBox never spread out children across the opposing orientation
(i.e. it never grew "lines" larger then their natural width, they would
act as if set to GTK_WRAP_BOX_SPREAD_START, now they are completely configurable).
This was added to the test only for the sake of making it
easier to reproduce a bug with scrolled windows (bug 629778).
Expected behaviour: The vertical scrollbar should dissapear as soon
as the required height for the full allocation width (without any
vertical scrollbar) is small enough to not need a scrollbar.
Made an enum GtkWrapBoxPacking for the expand/fill horizontal/vertical
boolean options... changed xpadding/ypadding to be horizontal-padding
and vertical-padding for a more consistent api and better readablility.
