to avoid hanging in cleanup().

oct(0) should return '0', not '00'

* timemodule.c: the mac has no unistd.h
* classobject.c: fixed several cases of return NULL that should be
  return -1 !!!

  coercion is now completely generic.
* ceval.c: for instances, don't coerce for + and *; * reverses
  arguments if left one is non-instance numeric and right one sequence.

  the type object.

Real changes:
(a) added section on special class methods.
(b) corrected typos spotted by Stoffel Erasmus.

by special syntax: you can now define your own numbers, sequences and
mappings.

posixpath.py: added undocumented expanndvars() (expands $VAR in string).

posixmodule.c: waitpid() is separate

added gettext() method to TextEdit.py;
fixed string.atoi() to ignore leading zeros.

* socketmodule.c: get rid of makepair(); fix makesocketaddr to fix
  broken recvfrom()
* socketmodule: get rid of getStrarg()
* ceval.h: move eval_code() to new file eval.h, so compile.h is no
  longer needed.
* ceval.c: move thread comments to ceval.h; always make save/restore
  thread functions available (for dynloaded modules)
* cdmodule.c, listobject.c: don't include compile.h
* flmodule.c: include ceval.h
* import.c: include eval.h instead of ceval.h
* cgen.py: add forground(); noport(); winopen(""); to initgl().
* bltinmodule.c, socketmodule.c, fileobject.c, posixmodule.c,
  selectmodule.c:
  adapt to threads (add BGN/END SAVE macros)
* stdwinmodule.c: adapt to threads and use a special stdwin lock.
* pythonmain.c: don't include getpythonpath().
* pythonrun.c: use BGN/END SAVE instead of direct calls; also more
  BGN/END SAVE calls etc.
* thread.c: bigger stack size for sun; change exit() to _exit()
* threadmodule.c: use BGN/END SAVE macros where possible
* timemodule.c: adapt better to threads; use BGN/END SAVE; add
  longsleep internal function if BSD_TIME; cosmetics