Make dirtybench run on Windows
Oops, need env.close() too.
CFFI: fix Cursor.putmulti()
CFFI: make Cursor be a context manager.
CFFI: remove all weakref use

This seems to be the final solution to the weakref performance problems
on CFFI: simply don't use them whatsoever. Now Cursor must be a context
manager, in order to ensure its .close() is called correctly.

At least user scripts will leak fast, so not using with: should be easy
to diagnose.
CFFI: inline remaining dependency management bits
CPython: Cursor.__enter__/Cursor.__exit__.
Implement Environment.__enter__/__exit__. Closes #54
Update ChangeLog.
3.x tests fix.
Transaction context manager test.
CPython: collapse away string indirection

Before:
    __TEXT  __DATA  __OBJC  others  dec hex
    81920   8192    0   40960   131072  20000

After:
    __TEXT  __DATA  __OBJC  others  dec hex
    81920   12288   0   40960   135168  21000
CPython: reorder argspec array to improve packing

Before:
    __TEXT      __DATA  __OBJC  others  dec     hex
    22090       7360    0       75191   104641  198c1

After:
    __TEXT      __DATA  __OBJC  others  dec     hex
    22082       6688    0       75191   103961  19619
fix link to master
Update doc notes around use of weakrefs.
cf331ccb @ git://git.openldap.org/openldap.git

* LMDB 0.9.13
* ITS#7771
* ITS#7793
* ITS#7834
* ITS#7861
* ITS#7875
Cursor context manager test
make test run on 2.5
Update Changelog
More context manager notes.