actually necessary for functionality, but good for transition.

- New semantics for __exit__() -- it must re-raise the exception
  if type is not None; the with-statement itself doesn't do this.
  (See the updated PEP for motivation.)

- Added context managers to:
  - file
  - thread.LockType
  - threading.{Lock,RLock,Condition,Semaphore,BoundedSemaphore}
  - decimal.Context

- Added contextlib.py, which defines @contextmanager, nested(), closing().

- Unit tests all around; bot no docs yet.

in multiple places. This makes compile()/eval()/etc also inherit the
absolute-import codeflag, like division and with-statement already were.

No good way to extract output yet.

Neal.

Add directory which contains known ref leaks.  Some of these are likely to be system dependent (like test_gestalt).

print the status so far and suppress printing the exception (but still exit).

Clarify intended use of set_context() and check errors at all call sites.

Replace the toy arena implementation with a real one,
based on allocating 8K chunks of memory by default.

from Tools/compiler/ast.txt are not used anywhere else in asttable.txt.
So remove "\&".

 - IMPORT_NAME takes an extra argument from the stack: the relativeness of
   the import. Only passed to __import__ when it's not -1.

 - __import__() takes an optional 5th argument for the same thing; it
   __defaults to -1 (old semantics: try relative, then absolute)

 - 'from . import name' imports name (be it module or regular attribute)
   from the current module's *package*. Likewise, 'from .module import name'
   will import name from a sibling to the current module.

 - Importing from outside a package is not allowed; 'from . import sys' in a
   toplevel module will not work, nor will 'from .. import sys' in a
   (single-level) package.

 - 'from __future__ import absolute_import' will turn on the new semantics
   for import and from-import: imports will be absolute, except for
   from-import with dots.

Includes tests for regular imports and importhooks, parser changes and a
NEWS item, but no compiler-package changes or documentation changes.

Sigh -- we really should have one place for all opcode metadata.

Jeremy, please review!