bootstrap: Support Markdown format NEWS files.

* build-aux/bootstrap.in (func_ensure_NEWS): New function to
link NEWS.md or similar to NEWS if necessary.
(funct_reconfigure): Use it.
* bootstrap: Regenerate.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
extract-trace: capture tool exit statuses correctly.

Depending on the shell, after executing a pipeline, $? is not
always the status of the first pipeline element.
* build-aux/extract-trace (func_tool_version_number): Move sed
command to a separate command invocation to ensure $? is not
corrupted before capture.
* bootstrap: Regenerate.

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