
	- clean up
	? check low memory conditions
	? 24-bit version

	Differences to the original BSL version

		- Replaced # (not) operator by NOT.
		- Replaced  IF A,B  with  IF A AND B.
		- Added OR operator.

		- Documented string variable subscripts
		  (already worked before).

		- Made IOCTL a command and its "function"
		  argument a string instead of a magic integer.

		- Replaced CMPS( (compare strings) function with
		  relational operators (=,<>,<,etc).

		- Added the POS( (string position) function.

		- Added control commands:
			WHILE / WEND,
			IF / THEN / ELSE / ENDIF,
			REPEAT / UNTIL,
			ON / GOTO,
			GOSUB / WITH.

		- Removed CALL command

		- Added CALL( operator (GOSUB variant for use in
		  expressions).

		- Added local scopes with LOCAL / ENDLOC.

		- Added function definitions (DEF FN(X) = ...).

		- Made LET accept multiple assignments.

		- Added FRE( (free memory) function.

		- Added EOF( (end of file) function.

		- Added ABS( (absolute value) function.

		- Added RND( (pseudo random number) function.

		- Added I/O commands: OPEN, CLOSE, ERASE (open, close,
		  erase file).

		- Added interactive commands:
			FILES (list open files),
			RENUM (renumber programs),
			INSERT (insert multiple lines),
			DELETE (delete lines),
			MOVE (move lines),
			COPY (copy lines),
			SEARCH (search comments).

		- Made RUN accept an optional entry point.

		- Added overflow checking to numeric expressions.

		- Made ? a shortcut for PRINT.

		- Added / command (list 20 lines at a given position
		  and memorize position).

		- Added : command (invoke line editor).

		- Added < and > commands for paging back/forward.

		- Made LIST and friends pretty-print the code.

		- Added LABEL and symbolic destinations to GOTO,
		  GOSUB, CALL, RESTORE.

		- Made RETURN clean up LOCALs.

		- Addex EXIT (exit from loop) command.
