sys.tracebacklimit.
* tut.tex (Exceptions): change text printed by traceback.
* lib5.tex (audioop): added minmax.
* lib5.tex (audioop.getsample): move wandered paragraph back
* lib3.tex, partparse.py: undo mucking with \nopagebreak (didn't work).
* partparse.py: ignore \nopagebreak command
* ref5.tex: added description of lambda forms.
* ref7.tex: added reference to lambda forms to section on function
  definition.
* lib1.tex: removed lambda as built-in function (it is now a special
  form).  Also removed feature of filter, map, reduce to turn a string
  argument into an anonymous function.