libctf: fix cv-qualified unnamed struct/union field lookup

libctf: fix cv-qualified unnamed struct/union field lookup

GCC permits not only unnamed structs and unions, but cv-qualified ones.
Our earlier fix in 6c3a38777b38a2ad87e2b2bcec4567578d1c83ec supported
unnamed structs and unions, but only unqualified ones.

Resolving away cvr-quals of nameless fields (and, irrelevantly, typedefs)
is easy and fixes this problem.

Tests adjusted accordingly.

libctf/
	PR libctf/32746
	* ctf-types.c (ctf_member_next): Resolve away cv-quals.
	(ctf_member_info): Likewise.
	* testsuite/libctf-lookup/struct-iteration-ctf.c: Add a cv-qualified
	type or two: make sure to keep a non-qualified one.
	* testsuite/libctf-lookup/struct-iteration.c: Verify consistency
	of ctf_member_next and ctf_member_info.
	* testsuite/libctf-lookup/struct-iteration.lk: Adjust.

Tested-by: Stephen Brennan <stephen.s.brennan@oracle.com>