* The recent addition of empty readtables broke named-readtables
fundamentally. Thanks for David Crawford for pointing that out.
I had to accomodate MERGE-READTABLES-INTO now that the neutral
element is no longer the standard readtable, but an empty
* We no make the readtable empty first when redefining it via a
DEFREADTABLE form. Then the content is refilled.
* MERGE-READTABLES-INTO now signals a new error
READER-MACRO-CONFLICT if a macro character is present
in more than one of the argument readtables.
DEFREADTABLE turns READER-MACRO-CONFLICT into a warning.
* Fix expansion of DEFREADTABLE so calls to MERGE-READTABLES-INTO
properly quote readtable names.
* Add WITHOUT-PACKAGE-LOCK for our :AROUND method of PRINT-OBJECT
specializing on READTABLE.
* Update docstrings accordingly.