PR gdb/8869:
* language.c (language_completer): New function.
(range_or_type_completer): New function.
(case_completer): New function.
(_initialize_language): Set completers.
* cli/cli-decode.c (add_setshow_string_cmd): Return the "set"
command.
(add_setshow_string_noescape_cmd): Likewise.
(add_setshow_integer_cmd): Likewise.
(add_setshow_uinteger_cmd): Likewise.
(add_setshow_zinteger_cmd): Likewise.
(add_setshow_zuinteger_cmd): Likewise.
* command.h (add_setshow_string_cmd,
add_setshow_string_noescape_cmd, add_setshow_uinteger_cmd,
add_setshow_zinteger_cmd, add_setshow_zuinteger_cmd): Update.