Do not forget to peel qualified type off when peeling types

Do not forget to peel qualified type off when peeling types

When peeling off typedefs, references and pointers to see if a type is
made of a class type, we forget to peel qualified types off.

This is in the context of parsing type info from DWARF and to
determine if we should delay type canonicalization (because a given
type is made of a class) or not.

Fixed thus.

	* include/abg-fwd.h (peel_qualified_type): Declare new function
	...
	* src/abg-ir.cc (peel_qualified_type): ... and define it.
	(peel_typedef_pointer_or_reference_type): Peel qualified types
	here too.

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