Factorize basic redundancy detection in diff report

Factorize basic redundancy detection in diff report

	* src/abg-comparison.cc
	(RETURN_IF_BEING_REPORTED_OR_WAS_REPORTED_EARLIER)
	(RETURN_IF_BEING_REPORTED_OR_WAS_REPORTED_EARLIER{2,3}): New
	macros.
	({pointer_diff, array_diff, reference_diff, qualified_type_diff,
	class_diff, typedef_diff}::report): Use the new macros above.
	* tests/data/test-bidiff/test-qual-type0-report.txt: Adjust
	because type pretty representation are now always quoted.
	* tests/data/test-bidiff/test-struct1-report.txt: Adjust likewise.

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