* builds/unix/configure.raw (ftoption_set, ftoption_unset): New
auxiliary functions to construct...
(FTOPTION_H_SED): ... this new variable.
Apply it as a sed argument while copying `ftoption.h' to the
`builds/unix' directory (using `AC_CONFIG_FILES').
Simplify code of test that checks cpp's computation of bit length
(the test previously created an empty `ftoption.h' file and deleted
it immediately afterwards); without this change, it can happen on my
GNU/Linux box that `configure's execution of `config.status' doesn't
create `ftoption.h' (no idea why this happens).
* builds/unix/install.mk (install): Install
`builds/unix/ftoption.h'.
* builds/unix/unix-def.in (DISTCLEAN): Updated.
* builds/unix/.gitignore: Updated.
8f4851997b