30-OCT-01 Fixed Bugs in file interp.c :

1. division (/) by zero when one or both operands are floats

2. fremove and frename gave wrong truth value
   (now success => true)

3. nullary, unary, binary, ternary had two bugs:

   1. coredump when there was nothing to push
      e.g. 11 22 [pop pop] nullary

   2. produced circular ("infinite") list when no
      new node had been created
      e.g. 11 22 [pop] nullary

4. app4 combinator was wrong.
   Also renamed: app2 -> unary2, app3 -> unary3, app4 -> unary4
   the old names can still be used, but are declared obsolete.

5. Small additions to (raw) Joy:

   1. putchars – previously defined in library file inilib.joy

   2. fputchars (analogous, for specified file)
      fputstring (== fputchars for Heiko Kuhrt's program)