[Patches] Add crc32() method to binascii

[Tim Peters]

> This patch adds a new method to module binascii.  It calculates
> a CRC-32 checksum. ...

Notes on this patch:

+ Format:  The crc_32_tab initializer extends thru column 96; it shouldn't
go beyond column 80.

+ Semantics:  "UL" should be appended to all unsigned long literals, to
prevent surprises on 64-bit machines (untagged literals are ints in C, and
0xFFF... is -1 on most machines, even the 64-bit ones).  Note that this
includes all the literals in the crc_32_tab initializer.

+ Test:  "If it's not tested, it's broken."  A test of this function needs
to be added to the std test suite.

> This method is generally useful, and is
> required for ZIP file checksums.  Use as follows:
>
>   print binascii.crc32("hello world")
>   # Or, in two pieces:
>   crc = binascii.crc32("hello")
>   crc = binascii.crc32(" world", crc)
>   print crc

This example should be in the docs, not in checkin mail commentary.  I
couldn't guess from the docs that this is supported usage (although I can
reverse-engineer it from the code).

pickily y'rs  - tim