extract-trace: find newest version of tool being searched for.

When a user has masked a better version of GNU M4 later in the
path by either an older version or a non-GNU M4 earlier in their
path, keep testing version numbers and use the best one from any
place it can be found.
* extract-trace (func_tool_version_number): Extract the last
word starting with a digit from first line of `tool --version`
output.
(func_find_tool): Use it to compare version output of matches,
preferring highest version number given a choice or else the
first matching tool name in PATH if no version ouput is generated.
(func_tool_version_output): Move definition before first caller.
* bootstrap: Regenerate.
Reported by Bob Friesenhahn
configury: add a Makefile to regenerate bootstrap.

* Makefile: New file.

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