* r4rs.scm: update primitive-load usage.
Don't define read-sharp.
* boot-9.scm: use read-hash-extend to install extra read syntax.
(read-sharp): removed.
Adjust usage of primitive-load-path, read, which no longer take
case_i or read-sharp arguments.
(macroexpand-1, macroexpand): Use local-ref instead of defined?
and eval.
* r4rs.scm (%load-verbosely): Use "module-defined?" instead of
"defined?".
* slib.scm (defined?): New function to take the place of the
builtin "defined?". It allways examines the slib module.