Some licensing-related housekeeping

[musicinmybrain]

Replace deprecated LGPL-3.0 SPDX identifier with [LGPL-3.0-or-later](https://spdx.org/licenses/LGPL-3.0-or-later].

Using LGPL-3.0-or-later instead of LGPL-3.0-only is based on the “any later version” language in the source-file headers, e.g.

priority-queue/src/lib.rs

Lines 5 to 9 in efe31e8

	* This program is free software: you can redistribute it and/or modify
	* it under the terms of the GNU Lesser General Public License as published by
	* the Free Software Foundation, either version 3 of the License, or
	* (at your option) any later version, or (at your opinion) under the terms
	* of the Mozilla Public License version 2.0.

although I note that in #23, contributors were asked about “LGPL 3” but not about later versions. If you believe this should be LGPL-3.0-only, let me know and I’ll revise the PR.

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Add MPL-2.0 “Exhibit A” text to source file headers, option “(a)” from #48.

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Fix a minor typo in license/copyright headers throughout the project, which said “at your opinion” rather than “at your option.”

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Copy the standard license/copyright comment from the other files to test-nostd/src/lib.rs.

@garro95 @ijackson

[garro95]

Thank you for your contribution.

I should have probably used a more specific wording in the question in #23.

Although, considering that the contributions were already under the terms of the LGPL-3.0-or-later before #23 and that the question was about adding the MPL, I think it's safe to assume that all the contributors are happy with the current double licensing under LGPL 3 or later or MPL 2.0

[musicinmybrain]

Thank you for your contribution.

Thanks for reviewing this quickly! Having these details worked out makes it much easier for me to package this crate for Fedora as part of the dependency tree for uv.

I should have probably used a more specific wording in the question in #23.

Although, considering that the contributions were already under the terms of the LGPL-3.0-or-later before #23 and that the question was about adding the MPL, I think it's safe to assume that all the contributors are happy with the current double licensing under LGPL 3 or later or MPL 2.0

That’s a good point. I agree.