* module/ice-9/mapping.scm (mapping-create-handle!): INIT is required.
(mapping-ref): Rewrite. Fix problem with DFLT.
(hash-table-mapping-hooks): Drop DELETE-PROC, hash-table accessors
only use ASSOC-PROC. Add INIT to create-handle hook. Use correct
hash-table accessors.
(make-hash-table-mapping): Drop DELETE-PROC.
(hash-table-mapping): Rewrite. Drop DELETE-PROC.
Moved ice-9/ and oop/ under module/, with the idea being that we have
only scheme under module/. Adjusted configure.in and Makefile.am
appropriately. Put oop/ at the end of the compilation order.