* lib/m4sugar/m4sugar.m4 (m4_defun_once): Avoid redundant blank
line when a defun_once macro is required.
(_m4_defun_once): New helper macro, for less memory use.
* tests/m4sugar.at (m4@&t@_require: nested): Adjust test.
Signed-off-by: Eric Blake <ebb9@byu.net>