std-autogen: avoid linking, instead copy autoconf files
std-autogen: avoid linking, instead copy autoconf files

This enables building source tarballs with build systems
that do not flatten the symlinks on tarball build,
eg: python distutils.

markokr/libusual,mgjv/libusual,ifduyue/libusual,markokr/libusual,rabbitt/libusual,mgjv/libusual,rabbitt/libusual,markokr/libusual,markokr/libusual,mgjv/libusual,rabbitt/libusual,ifduyue/libusual,rabbitt/libusual,mgjv/libusual,ifduyue/libusual,ifduyue/libusual