completion_list_add_name wrapper functions

Replace macros with functions.

gdb/ChangeLog:
2017-06-27  Pedro Alves  <palves@redhat.com>

	* symtab.c (COMPLETION_LIST_ADD_SYMBOL)
	(MCOMPLETION_LIST_ADD_SYMBOL): Delete macros, replace with ...
	(completion_list_add_symbol, completion_list_add_msymbol):
	... these new functions.
	(add_symtab_completions)
	(default_make_symbol_completion_list_break_on_1): Adjust.