Fixed problems with combination of height-for-width apis and

Fixed problems with combination of height-for-width apis and
alignment/margin vfuncs adjust_size_request/allocation

Now get_height_for_width() will internally update the for_width
before passing it to the real height_for_width() vfunc, allowing
margins and extra space for alignments to be stripped, thus requesting
sufficient height for greater than natural widths (and also accounting
for margins properly). Test case adjusted in testadjustsize to ensure
proper behavior.