Update license headers and remove redundant file name comment.

[iphydf]

"All rights reserved" was incorrect. The project was licensed under GPL3,
which means a lot of rights are licensed to everybody in the world, i.e.
not reserved to the "Tox Project".

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This change is 

[fcore117]

Reviewed 90 of 90 files at r1.
Review status: all files reviewed at latest revision, all discussions resolved, some commit checks failed.

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Comments from Reviewable

[robinlinden]

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Reviewed 90 of 90 files at r1.
Review status: all files reviewed at latest revision, 1 unresolved discussion.

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toxcore/util.c, line 5 at r1 (raw file):

 *
 * This file is donated to the Tox Project.
 * Copyright 2013  plutooo

You didn't remove this person's name from any other files. Is this intentional?

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Comments from Reviewable

[iphydf]

Review status: 89 of 90 files reviewed at latest revision, 1 unresolved discussion.

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toxcore/util.c, line 5 at r1 (raw file):

Previously, robinlinden (Robin Lindén) wrote…

You didn't remove this person's name from any other files. Is this intentional?

No, added back.

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Comments from Reviewable

[robinlinden]

Reviewed 1 of 1 files at r2.
Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[nurupo]

testing/av_test.c, line 22 at r2 (raw file):

 *   Compile with (Linux only; in newly created directory toxcore/dir_name):
 *   gcc -o av_test ../toxav/av_test.c ../build/.libs/libtox*.a -lopencv_core \
 *   -lopencv_highgui -lopencv_imgproc -lsndfile -pthread -lvpx -lopus -lsodium -lportaudio

Was this intentionally removed?

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Comments from Reviewable

[nurupo]

toxcore/crypto_core_mem.c, line 21 at r2 (raw file):

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

Unrelated change.

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Comments from Reviewable

[nurupo]

toxav/ring_buffer.c, line 4 at r2 (raw file):

 * Copyright © 2016-2017 The TokTok team.
 * Copyright © 2013 Tox project.
 * Copyright © 2013 plutooo

What pluto has to do with toxav?

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Comments from Reviewable

[nurupo]

toxcore/crypto_core_mem.c, line 21 at r2 (raw file):

Previously, nurupo wrote…

Unrelated change.

There are actually quite of few like this.

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Comments from Reviewable

[nurupo]

Is the unicode copyright symbol somehow better than (c) or (C)?

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Comments from Reviewable