Eliminate make_symbol_overload_list-related globals & cleanup

This gets rid of a few globals and a cleanup.

make_symbol_overload_list & friends currently maintain a global
open-coded vector.  Reimplement that with a std::vector, trickled down
through the functions.  Rename a few functions from "make_" to "add_"
for clarity.

gdb/ChangeLog:
2018-11-21  Pedro Alves  <palves@redhat.com>

	* cp-support.c (sym_return_val_size, sym_return_val_index)
	(sym_return_val): Delete.
	(overload_list_add_symbol): Add std::vector parameter.  Adjust to
	add to the vector.
	(make_symbol_overload_list): Adjust to return a std::vector
	instead of maintaining a global open coded vector.
	(make_symbol_overload_list_block): Add std::vector parameter.
	(make_symbol_overload_list_block): Rename to ...
	(add_symbol_overload_list_block): ... this and add std::vector
	parameter.
	(make_symbol_overload_list_namespace): Rename to ...
	(add_symbol_overload_list_namespace): ... this and add std::vector
	parameter.
	(make_symbol_overload_list_adl_namespace): Rename to ...
	(add_symbol_overload_list_adl_namespace): ... this and add
	std::vector parameter.
	(make_symbol_overload_list_adl): Delete.
	(add_symbol_overload_list_adl): New.
	(make_symbol_overload_list_using): Rename to ...
	(add_symbol_overload_list_using): ... this and add std::vector
	parameter.
	(make_symbol_overload_list_qualified): Rename to ...
	(add_symbol_overload_list_qualified): ... this and add std::vector
	parameter.
	* cp-support.h: Include "common/array-view.h" and <vector>.
	(make_symbol_overload_list): Change return type to std::vector.
	(make_symbol_overload_list_adl): Delete declaration.
	(add_symbol_overload_list_adl): New declaration.
	* valops.c (find_overload_match): Local 'oload_syms' now a
	std::vector.
	(find_oload_champ_namespace): 'oload_syms' parameter now a
	std::vector pointer.
	(find_oload_champ_namespace_loop): 'oload_syms' parameter now a
	std::vector pointer.  Adjust to new make_symbol_overload_list
	interface.