Problems were; in FREE mode there was a simple typo where we were
repeatedly checking the size of the same item in get_largest_line_length(),
and in ALIGNED mode we were assuming something like HOMOGENEOUS which
was incorrect; added get_largest_aligned_line_length() which properly
adds up the collective max sizes of every index in the line.
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).
With this new approach at request and allocate time, the average child size
is used to determine a good guess at how many columns will fit the box
width; afterwards extra columns are appended and checked to fit.
Then the row heights are calculated based on height-for-width of each
child in the row which now may have individual widths.
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.
