Sequences read from ABIF files have to be coerced to strings.
Let's actually use our own DEFCONSTANT macro.
Updated the dependencies.
Small changes:
1. Doc-string was updated for the TOPLEVEL function.
2. We always create and select a default workspace during the
   start-up.
3. In case of an unsupported CL implementation, BUILD function will
   say it doesn't support it _yet_ - this way it sounds much better,
   doesn't it?
Some changes in the package interfaces.
- GAS-UTILS exports a SPLIT utility function;
- GAS-UI has now some more generic functions for user interface
  implementations to implement.
Updated MAKE-NGRAM to use the GAS-DNA:DNA-STRING type.
A major step forward in the command-driven interface:
1. commands can now take arbitrary numbers of arguments;
2. they are also compiled (at the time of definition);
3. commands "m" (match) and "edit" were added;
4. user-interface protocol was extended, but it's full potential isn't
   used yet.