Only show leaf type changes in the leaf type changes section

Only show leaf type changes in the leaf type changes section

The leaf report is somewhat messy in that we show all kinds of leaf
artifact changes in the section where we should only show leaf type
changes.

This commit fixes that.

This patch is part of the set of patches whose titles are:

    Do not show decl-only-to-def changes in the leaf reporter
    Overhaul of the report diff stats summary
    Do not mark "distinct" diff nodes as being redundant
    Fix meaning of "harmless name change" to avoid overfiltering
    Better handle category propagation of pointer changes
    Improve function changes reporting in leaf and default mode
    Don't filter out typedef changes with redundant underlying type changes
    Only show leaf type changes in the leaf type changes section
    Fix leaf report of class data member changes
    Always show redundant changes in leaf mode
    Avoid reporting an enum change if it has already been reported
    When we say an a change was reported earlier give its source location
    [abipkgdiff]: in leaf mode we always show redundant changes
    Update tests for the "better leaf mode redundancy management" patchset

	* src/abg-leaf-reporter.cc (report_type_changes_from_diff_maps):
	Split this out from leaf_reporter::report_changes_from_diff_maps
	and make it report only about leaf *type* changes.
	(leaf_reporter::report_changes_from_diff_maps): Use the new
	report_type_changes_from_diff_maps function.
	(leaf_reporter::report): In the overload for corpus_diff, use the
	new report_type_changes_from_diff_maps function, instead of the
	report_changes_from_diff_maps function.

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