generated, check that the record is the right type and throw an error
if not, as per srfi-9 spec. Previously a different record type
resulted in #f from an accessor and silently doing nothing in
modifier.
srfi-11.scm, srfi-14.scm, srfi-16.scm: Move module the system
directives `export', `export-syntax', `re-export' and
`re-export-syntax' into the `define-module' form. This is the
recommended way of exporting bindings.
* srfi-19.scm, srfi-17.scm, srfi-16.scm, srfi-14.scm, srfi-13.scm,
srfi-11.scm, srfi-10.scm, srfi-9.scm, srfi-8.scm, srfi-6.scm,
srfi-2.scm: Use `cond-expand-provide' for providing features to
`cond-expand'.
