ARM optimized insert_string

Using a faster hash function yields a considerable performance boost
in compression (average 8% on A53 and 24% on A72).

This change was enabled by previous patch with optimized crc32 using
ARMv8-1 crypto extensions for performing CPU feature detection
(so won't help older ARMv7 SoCs).

Bug: 873759
Change-Id: I88ece549a63d923beef4f96a046acdf09e529784
Reviewed-on: https://chromium-review.googlesource.com/1173262


Reviewed-by: Chris Blume <cblume@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#583113}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 1364a33fe0f2b9588a2d018f62ff4d966a525f37