Rename configure.in to configure.ac

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash-docs/trunk@23532 57a11ea4-9604-0410-9ed3-97b8803252fd
Bug 688579 - Run xmllint or variant in make distcheck

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash-docs/trunk@23533 57a11ea4-9604-0410-9ed3-97b8803252fd