Fix spurious type size change report for distinct_diff

Fix spurious type size change report for distinct_diff

When looking at diff of two distinct types it can happen that the
change report mentions a type size change even when the two type sizes
are equal.

This patch fixes that.

	* src/abg-comparison.cc (report_size_and_alignment_changes):
	Report size change only when the sizes are different.
	* tests/data/test-diff-filter/test33-report-0.txt: Adjust.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>