Slightly unbreak named-readtables per my latest changes.

The compatibility API that is exposed for dispatching characters
can coerce fdefns to symbols, but there is still a problem that
non-dispatching character functions are groveled out and passed
to SET-MACRO-CHARACTER which won't work in general.

Related problem in sb-cover - it did not understand that
GET-MACRO-CHARACTER could return a function-designator.
Remove another 100KB of junk strings from the image.
Silence "unable to dx-allocate" notes from MAPfoo transforms