Implement P0305R1, Selection statements with initializer.

Implement P0305R1, Selection statements with initializer.

	* cp-array-notation.c (create_an_loop): Call finish_init_stmt
	instead of finish_for_init_stmt.
	* cp-tree.h (finish_for_init_stmt): Rename to finish_init_stmt.
	* decl.c (poplevel): Adjust a comment.
	* init.c (build_vec_init): Call finish_init_stmt instead of
	finish_for_init_stmt.
	* name-lookup.c (pushdecl_maybe_friend_1): Adjust a comment.
	* name-lookup.h (enum scope_kind): Likewise.
	* parser.c (cp_parser_statement): Update commentary.
	(cp_parser_init_statement_p): New function.
	(cp_parser_selection_statement): Parse the optional init-statement.
	(cp_parser_for): Call finish_init_stmt instead of finish_for_init_stmt.
	(cp_parser_c_for): Likewise.
	(cp_convert_range_for): Call finish_init_stmt instead of finish_for_init_stmt.
	(cp_parser_range_for_member_function): Update commentary.
	(cp_parser_iteration_statement):
	(cp_parser_for_init_statement): Rename to cp_parser_init_statement.
	* pt.c (tsubst_omp_for_iterator): Update commentary.
	(tsubst_expr): Call finish_init_stmt instead of finish_for_init_stmt.
	* semantics.c (finish_for_init_stmt): Rename to finish_init_stmt.
	Update commentary.

	* g++.dg/cpp1z/init-statement1.C: New test.
	* g++.dg/cpp1z/init-statement2.C: New test.
	* g++.dg/cpp1z/init-statement3.C: New test.
	* g++.dg/cpp1z/init-statement4.C: New test.
	* g++.dg/cpp1z/init-statement5.C: New test.
	* g++.dg/cpp1z/init-statement6.C: New test.
	* g++.dg/cpp1z/init-statement7.C: New test.
	* g++.dg/cpp1z/init-statement8.C: New test.

From-SVN: r240798