Simplify completion_list_add_name | remove sym_text / sym_text_len

Simplify completion_list_add_name | remove sym_text / sym_text_len

sym_text_len existed to strip parameters out of the lookup name.  Now
that that's handled by the lookup_name_info objects, the
sym_text/sym_text_len parameters are no longer necessary.

gdb/ChangeLog:
2017-11-08  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_make_symbol_completion_list): Remove text and
	text_len locals and don't pass them down.
	* symtab.c (completion_list_add_name): Remove
	sym_text/sym_text_len parameters and adjust.
	(completion_list_add_symbol, completion_list_add_msymbol)
	(completion_list_objc_symbol, completion_list_add_fields)
	(add_symtab_completions): Likewise.
	(default_collect_symbol_completion_matches_break_on)
	(collect_file_symbol_completion_matches): Remove sym_text_len
	local and don't pass it down.
	* symtab.h (completion_list_add_name): Remove
	sym_text/sym_text_len parameters.