* lib/m4sugar/m4sugar.m4 (m4_flatten): Only use regex if newline
is present.
(_m4_split): Avoid useless expansions inside definition. Move
argument defaulting...
(m4_split): ...here. Change alternate quote to something less
likely to appear in $1. Also, special case space as regexp...
(m4_foreach_w): ...to avoid regexp on single-term list.
(m4_default, m4_defn, m4_popdef, m4_undefine, _m4_foreach): Avoid
useless expansions inside definition.
* tests/m4sugar.at (m4@&t@_split): Add tests.
Signed-off-by: Eric Blake <ebb9@byu.net>
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