Remove typep and VEC(typep) from linespec.c

Remove typep and VEC(typep) from linespec.c

This removes VEC(typep) from linespec.c in favor of std::vector.  It
also removes the "typep" typedef.  This change allowed the removal of
some cleanups.

I believe the previous cleanup code in find_superclass_methods could
result in a memory leak, so this patch is an improvement in that way
as well.

ChangeLog
2018-04-05  Tom Tromey  <tom@tromey.com>

	* linespec.c (typep): Remove typedef.
	(find_methods, find_superclass_methods): Take a std::vector.
	(find_method): Use std::vector.