Change definition of `DEFINE_PRIMITIVE' macro to include extra fields

Change definition of `DEFINE_PRIMITIVE' macro to include extra fields
for minimum number of arguments and documentation.  Add primitive to
access the documentation string.  The min args slot is currently
unused.  Change all definitions of primitives to use this macro.

The documentation strings should be filled in as time permits.

Partially update "sample.c" to reflect this.  More work remains to be
done.

Update "Findprim.c" substantially, to handle these changes.  Also
change all fixed size tables to be dynamically allocated.

Define new macros `EMPTY_LIST', `SHARP_F' and `SHARP_T'.  All
references to `TRUTH' replaced by `SHARP_T'.  Some references to `NIL'
changed to the appropriate macro, but many more remain; these should
be replaced as time permits.

Update several copyright notices to reflect new year.

Change name of "primitive.h" to "prims.h".