xrefautomaticsectiontitle appears to be available from texinfo 5.0 or
greater.  As such, it is not worthwhile to add requirement for a minimum
necessary makeinfo version.  So remove the usage of it.

Also align node name with section title where possible.

ChangeLog:

	* libsframe/doc/sframe-spec.texi: Remove usage of
	xrefautomaticsectiontitle.