Fix CRC32 initialisation and finalisation

[g2p]

See #166.

[g2p]

There are still 6 failing tests if I run make && _build/lib_test/test.native test, but none that weren't failing before (mostly due to ECONNREFUSED).

[samoht]

Thanks!

Travis is running the "fast" tests only, I should probably change that. The other tests needs ./scripts/git-dumb-server to run in an other terminal.

[samoht]

Hum, I still have an issue with FS 11:

$ cd lib_test && ../_build/lib_test/test.native test FS 11
[..]
error: HEAD: not a commit
broken link from  commit 17498114d5eb1beb64418071025f0555887668ec
              to  commit cca30fe9644f6181a0aec72148f768f21a75eaa1
broken link from  commit 17498114d5eb1beb64418071025f0555887668ec
              to  commit 7c6760799c7845f565c9f29cccc02971e417f8c5
missing commit 7c6760799c7845f565c9f29cccc02971e417f8c5
missing commit cca30fe9644f6181a0aec72148f768f21a75eaa1
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
ASSERT fsck
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[failure] Error fsck: expecting 0, got 10.

[samoht]

I seems to see it with previous versions of ocaml-git too, so that's not related to your patch. Seems that the new commits exposed a real bug somewhere else... (the "slow" unit tests clone this repository with various options) ... Interesting!

[samoht]

So it seems that this is due to the fact that ocaml-git doens't create shallow Git repository correctly (this is related to #45), ie. we understand, read and unpack shallow pack files, but we don't create the right shallow metadata in .git/* so git fsck becomes very confused.

So not a regression, and the new crc code seems to work quite right! Thanks!