Delay canonicalization for array and qualified types

Delay canonicalization for array and qualified types

Array and qualified types can be edited after they are built, e.g, to
fold the qualifiers of the array as those should always apply to the
element types of the array, at least in C and C++.  So we need to
delay the canonicalization of these types until *after* all that type
editing is done.  We were not doing that properly and I suspect this
is the cause of some "heisenregressions" we are seeing on some
platforms intermittently.

This patch does delay the type canonicalization and insures that we
don't edit types that are canonicalized already.

	* src/abg-dwarf-reader.cc (maybe_canonicalize_type): Delay the
	canonicalization of array and qualified types, just like what we
	do for classes and function types already.
	(maybe_strip_qualification):  Do not
	re-canonicalize array and qualified types here because it should
	not be necessary anymore.

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