Add third_party/wuffs

Skia (https://skia.googlesource.com/skia) is a 2-D graphics library,
already in use by Chromium as third_party/skia. Wuffs
(https://github.com/google/wuffs) is a memory-safe programming language
whose standard library includes a GIF image decoder. Wuffs' standard
library is also available as transpiled C code. From Skia's (and
Chromium's) point of view, Wuffs' standard library is just another C
library. It's just not hand-written C.

Upstream Skia is moving to use Wuffs for GIF image decoding
(https://bugs.chromium.org/p/skia/issues/detail?id=8235). For Chromium,
this commit (adding third_party/wuffs, but no change in the generated
binaries yet) is the first in a series of commits (see
crbug.com/1014044) to have Skia-in-Chromium also use Wuffs.

Wuffs is released under the Apache License 2.0:
https://github.com/google/wuffs/blob/master/LICENSE

Bug: 1014044
Change-Id: I6b41794af09b07aacc48d519651bc397e761ad71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1859536
Reviewed-by: Chris Palmer <[email protected]>
Reviewed-by: Matthew Denton <[email protected]>
Reviewed-by: Nico Weber <[email protected]>
Commit-Queue: Nigel Tao <[email protected]>
Cr-Commit-Position: refs/heads/master@{#708485}
6 files changed