Partial m4sugar merge from autoconf: m4_map.

* data/m4sugar/m4sugar.m4 (m4_fst): Delete.
(m4_map, m4_map_sep, _m4_map): Rewrite more efficiently.
(m4_apply, _m4_apply, m4_mapall, m4_mapall_sep): New macros.
* data/java.m4 (b4_token_enums): Use more efficient short-circuit
for empty list.
* data/c.m4 (b4_token_defines, b4_token_enums, b4_c_ansi_formals):
Likewise.
(b4_parse_param_for): Avoid m4_fst, now that autoconf no longer
declares it.

Signed-off-by: Eric Blake <ebb9@byu.net>