Add warnings for unsupported `simple-format' options.

Add warnings for unsupported `simple-format' options.

* module/language/tree-il/analyze.scm
  (format-analysis)[check-simple-format-args]: New procedure.  Use it.
  Add support for applications of <module-ref>.

* module/system/base/message.scm (%warning-types): Handle the `format
  simple-format' warning.

* module/language/scheme/spec.scm (scheme)[make-default-environment]:
  Use `simple-format' as the default `format'.

* test-suite/tests/tree-il.test ("warnings")["format"]: Explicitly use
  (@ (ice-9 format) format) where needed.
  ("simple-format"): New test prefix.