libtool: split sco version into its own type.

* m4/libtool.m4 (_LT_SYS_DYNAMIC_LINKER): Set version type to
"sco" for sco based hosts.
* build-aux/ltmain.in (func_mode_link): Accept new "sco"
version_type as equivalent to freebsd-elf.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
libtool: use a modern library version scheme for freebsd-elf.

* m4/libtool.m4 (_LT_SYS_DYNAMIC_LINKER): Adopt downstream patch
used by FreeBSD for versioned library filenames.
* build-aux/ltmain.in (func_mode_link): Replace conflicting
freebsd-elf version_type case branches with a single calculation
setting major and versuffix to match downstream FreeBSD.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
gnulib: sync with upstream.

* gnulib: sync with upstream.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>