abg-writer: drop deprecated API

abg-writer: drop deprecated API

Drop the deprecated overloads for write_translation_unit, write_corpus,
write_corpus_group. Also remove the deprecation facilities as they are
not used anymore.

	* include/abg-fwd.h (ABG_DEPRECATED): Remove this macro.
	* include/abg-writer.h (write_translation_unit, write_corpus)
	(write_corpus_group): Drop the deprecated overloads of these
	declarations.
	* src/abg-writer.cc (write_translation_unit, write_corpus)
	(write_corpus_group): Drop the deprecated overloads of these
	definitions.

Signed-off-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Dodji Seketeli <dodji@redhat.com>