1.0.48.13: SET-SYNTAX-FROM-CHAR and dispatch-macro characterness

1.0.48.13: SET-SYNTAX-FROM-CHAR and dispatch-macro characterness

  Previously when the to-char was a dispatch-macro character in to-readtable,
  but from-char wasn't one in from-readtable, SET-SYNTAX-FROM-CHAR didn't do
  anything.

  CLHS says "If the character is a dispatching macro character, its entire
  dispatch table of reader macro functions is copied." which *can* be taken to
  mean that dispatch table should not be removed even if it doesn't exist at
  all in the from-readtable, but that interpretation doesn't really match with
  the rest of the description or the exhortation to copy the syntax type -- I
  read it as an instruction to copy the whole dispatch table, not just the
  fact that the character is a dispatching macro character.