objc++: Always pop scope with method definitions [PR97015]

objc++: Always pop scope with method definitions [PR97015]

Syntax errors in method definition lists could leave us in a function
scope.  My recent change for block scope externs didn't like that.
This reimplements the parsing loop to finish the method definition we
started.  AFAICT the original code was attempting to provide some
error recovery.  Also while there, simply do the token peeking at the
top of the loop, rather than at the two(!) ends.

	gcc/cp/
	* parser.c (cp_parser_objc_method_definition_list): Reimplement
	loop, make sure we pop scope.
	gcc/testsuite/
	* obj-c++.dg/syntax-error-9.mm: Adjust expected errors.