Create NsswitchReader

Reads /etc/nsswitch.conf files and parses tokens. Designed to be fairly
lenient and attempts to turn most unrecognized/unparsable input into
"unknown" output tokens.

Bug: 117655
Change-Id: Icab4e2aef501ab1e7d195747cc8c4d4d7a56a7b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2803074
Reviewed-by: Dan McArdle <dmcardle@chromium.org>
Commit-Queue: Eric Orth <ericorth@chromium.org>
Cr-Commit-Position: refs/heads/master@{#869626}
GitOrigin-RevId: 54ce38f58c504123862a2c85c084f8f0f9ada602
4 files changed