The old behaviour was to expect the user to go modify manually a source
file which is not a great idea because that's typically the kind of things
in charge of the configure script.
As a side effect, we can now use an automake conditional to avoid compiling
the source file in charge of the feature when not used, instead of trying
to compile an empty-looking file.
Signed-off-by: Christophe CURIS <christophe.curis@free.fr>
2ebfcd9c5c