deps: require Automake >= 1.9.6 in generated Makefile fragments

deps: require Automake >= 1.9.6 in generated Makefile fragments

That is the same minimal version required in the DEPENDENCIES file.
Moreover, the old code generated a requirement of Automake >= 1.5,
and that is an insanely outdated version.

* gnulib-tool: Bump minimal version requirement in AUTOMAKE_OPTIONS.
* tests/havelib/rpathlx/Makefile.am: Likewise.
* tests/havelib/rpathly/Makefile.am: Likewise.
* tests/havelib/rpathlyx/Makefile.am: Likewise.
* tests/havelib/rpathlz/Makefile.am: Likewise.
* tests/havelib/rpathlzyx/Makefile.am: Likewise.
* tests/havelib/rpathx/Makefile.am: Likewise.
* tests/havelib/rpathy/Makefile.am: Likewise.
* tests/havelib/rpathz/Makefile.am: Likewise.