* modules/roundl-ieee: New file.
* m4/roundl.m4 (gl_FUNC_ROUNDL): If gl_FUNC_ROUNDL_IEEE is also used,
test whether roundl works according to ISO C 99 with IEC 60559.
* m4/roundl-ieee.m4: New file.
* modules/roundl-ieee-tests: New file.
* tests/test-roundl-ieee.c: New file, based on tests/test-roundl.c.
* tests/test-roundl.c (main): Remove signbit tests.
* modules/roundl-tests (Depends-on): Remove signbit.
* doc/posix-functions/roundl.texi: Mention the new module.