reader: Remove useless support for WIP types

reader: Remove useless support for WIP types

In the abixml reader, WIP types are tracked to know if a type has been
fully constructed yet or not.  This information is later useful to
know if a given type should be canonicalized right away, or if its
canonicalization should be delayed until the entire abixml file has
been read.

Right now, with all the evolutions that happened in the abixml reader,
only scalar types are canonicalized right away.  All other types are
canonicalized late, meaning, after the entire abixml file is read.
This doesn't have any noticeable performance impact because the volume
of types coming from an abixml file is relatively small enough,
compared to what we can see in a DWARF/ELF binary due to type
duplication.

So the whole WIP tracking becomes is now pretty much useless, in
practise.  So this patch does away with it altogether.

	* src/abg-reader.cc (read_context::m_wip_types_map): Remove data
	member.
	(read_context::{clear_wip_classes_map, mark_type_as_wip,
	unmark_type_as_wip, is_wip_type}): Remove member functions.
	(read_context::maybe_canonicalize_type): Remove use of
	is_wip_type.

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