zlib: inflate using wider loads and stores

In inflate_fast() the output pointer always has plenty of room to write.  
This means that so long as the target is capable, wide un-aligned 
loads and stores can be used to transfer several bytes at once.

When the reference distance is too short simply unroll the data a 
little to increase the distance. Patch by Simon Hosie.

PNG decoding performance gains should be around 30-33%.

BUG=697280

Change-Id: I59854eb25d2b1e43561c8a2afaf9175bf10cf674
Reviewed-on: https://chromium-review.googlesource.com/627098


Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#497866}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: ad8fca9f4ad29ab87e49ec91a3577ef3696b3a84