Ignoring failures in AC_OUTPUT

[Kristis Makris]

Hello. Is there a way to tell autoconf to ignore failures by AC_OUTPUT
to create a file ? Right now, if one .in file is missing, autoconf
refuses to continue.

This feature could be useful when one is maintaining private sources
that need help from autoconf to autogenerate some Makefiles, but yet
should not be part of an official release of a project. These sources
could be for example a prototype of a researcher that does not want to
release his source. This prototype could be used by an autoconf-managed
project as part of testing, but should not be part of the public source
distribution.