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This CL adds Zucchini utilities related to parsing and printing, along
with tests. Details:
- LimitedOutputStream: Used for printing error messages without
  flooding console with output.
- AsHex: Syntactical sugar for iostream-printing of hex values.
- PrefixSep: Syntactical sugar for iostream-printing of list of values.
- EatChar and StrictUInt: Parse command line parameters. Will be used to
  parse imposed matches.

Bug: 729154
Change-Id: I232295419172a5b52cbb39cea89009a2e03fb684
Reviewed-on: https://chromium-review.googlesource.com/567265
Commit-Queue: Erik Chen <erikchen@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486019}