Use htab_eq_string in libctf

	* ctf-impl.h (ctf_dynset_eq_string): Don't declare.
	* ctf-hash.c (ctf_dynset_eq_string): Delete function.
	* ctf-dedup.c (make_set_element): Use htab_eq_string.
	(ctf_dedup_atoms_init, ADD_CITER, ctf_dedup_init): Likewise.
	(ctf_dedup_conflictify_unshared): Likewise.
	(ctf_dedup_walk_output_mapping): Likewise.