chore: make yuzu REUSE compliant

[REUSE] is a specification that aims at making file copyright
information consistent, so that it can be both human and machine
readable. It basically requires that all files have a header containing
copyright and licensing information. When this isn't possible, like
when dealing with binary assets, generated files or embedded third-party
dependencies, it is permitted to insert copyright information in the
`.reuse/dep5` file.

Oh, and it also requires that all the licenses used in the project are
present in the `LICENSES` folder, that's why the diff is so huge.
This can be done automatically with `reuse download --all`.

The `reuse` tool also contains a handy subcommand that analyzes the
project and tells whether or not the project is (still) compliant,
`reuse lint`.

Following REUSE has a few advantages over the current approach:

- Copyright information is easy to access for users / downstream
- Files like `dist/license.md` do not need to exist anymore, as
  `.reuse/dep5` is used instead
- `reuse lint` makes it easy to ensure that copyright information of
  files like binary assets / images is always accurate and up to date

To add copyright information of files that didn't have it I looked up
who committed what and when, for each file. As yuzu contributors do not
have to sign a CLA or similar I couldn't assume that copyright ownership
was of the "yuzu Emulator Project", so I used the name and/or email of
the commit author instead.

[REUSE]: https://reuse.software

Follow-up to 01cf05bc75b1e47beb08937439f3ed9339e7b254

2 files changed, 8 insertions, 0 deletions

diff --git a/externals/libusb/CMakeLists.txt b/externals/libusb/CMakeLists.txt
index 12bdc097a..055b89295 100644
--- a/externals/libusb/CMakeLists.txt
+++ b/externals/libusb/CMakeLists.txt
@@ -1,3 +1,6 @@
+# SPDX-FileCopyrightText: 2020 yuzu Emulator Project
+# SPDX-License-Identifier: GPL-2.0-or-later
+
 if (MINGW OR (${CMAKE_SYSTEM_NAME} MATCHES "Linux") OR APPLE)
     set(LIBUSB_FOUND ON CACHE BOOL "libusb is present" FORCE)
     set(LIBUSB_VERSION "1.0.24" CACHE STRING "libusb version string" FORCE)
diff --git a/externals/libusb/config.h.in b/externals/libusb/config.h.in
index 915b7390f..42ae5a5e8 100644
--- a/externals/libusb/config.h.in
+++ b/externals/libusb/config.h.in
@@ -1,3 +1,8 @@
+/* 
+ * SPDX-FileCopyrightText: 2020 yuzu Emulator Project
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
 /* Default visibility */
 #if defined(__GNUC__) || defined(__clang__)
   #define DEFAULT_VISIBILITY __attribute__((visibility("default")))