Explicitely detect anonymous data member changes

Explicitely detect anonymous data member changes

This patch detects when a data member becomes anonymous or when an
anonymous data member becomes non anonymous and emits an explicit
message.

	* include/abg-comp-filter.h (has_anonymous_data_member_change):
	Add new function declaration.
	* include/abg-fwd.h (is_data_member, is_anonymous_data_member):
	declare new overloads.
	* src/abg-comp-filter.cc (has_anonymous_data_member_change):
	Define new overloads.
	* src/abg-ir.cc (is_data_member, is_anonymous_data_member): Define
	new overloads.
	* src/abg-reporter-priv.cc (represent): In the var_diff overload,
	detect when we have anonymous data member changes and emit
	explicit error messages then.
	* tests/data/test-diff-dwarf/test45-anon-dm-change-report-0.txt:
	New test material.
	* tests/data/test-diff-dwarf/test45-anon-dm-change-v0.cc: Likewise.
	* tests/data/test-diff-dwarf/test45-anon-dm-change-v0.o: Likewise.
	* tests/data/test-diff-dwarf/test45-anon-dm-change-v1.cc: Likewise.
	* tests/data/test-diff-dwarf/test45-anon-dm-change-v1.o: Likewise.
	* tests/data/Makefile.am: Add the new test material above to source
	distribution.
	* tests/test-diff-dwarf.cc (in_out_specs): Add the new test
	material above to the test harness.
	* tests/data/test-diff-filter/test30-pr18904-rvalueref-report0.txt: Adjust.
	* tests/data/test-diff-filter/test30-pr18904-rvalueref-report1.txt: Likewise.
	* tests/data/test-diff-filter/test30-pr18904-rvalueref-report2.txt: Likewise.
	* tests/data/test-diff-filter/test35-pr18754-no-added-syms-report-0.txt: Likewise.

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