[crashers] Add license header: Apache License v2.0 with Runtime Library Exception

[practicalswift]

What's in this pull request?

This is a follow-up to PR #1649.

Add license header: Apache License v2.0 with Runtime Library Exception.

Approvals given in #1649.

Resolved bug number: –

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[tkremenek]

Is there a reason to put the reference to Apache 2 in every test file? The idea is that all the sources in the repository are under the Apache 2 license. It doesn't seem like an explicit reference to Apache 2 is needed, but just the standard preamble that appears in the majority of source files in the repository:

// This source file is part of the Swift.org open source project
// See http://swift.org/LICENSE.txt for license information

This also seems more maintainable in case there are ever any refinements/changes to the license. In such case, we only need to change LICENSE.txt, not every single file.

[MatejLach]

I agree with @tkremenek that this seems like a better way to do it.
Looking at other languages here on github, this is how Julia does it and they seem to be fine.

On the other hand, Rust specifies in every file which license they use, (like swift does now), and they also use Apache 2, but I don't think that is a requirement of the license so I'll just go with the Julia approach if possible.

[lattner]

Agreed, please keep with the canonical file header, that way we have consistency across the source base (it is also what lawyers have reviewed and approved).

[practicalswift]

@tkremenek @MatejLach @lattner Good points. I've now updated this PR. Looks good now? :-)

[lattner]

Please include the full header:

// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors

Thanks!

[practicalswift]

@lattner Updated - looks good now? :-)

[lattner]

Looks great! Thank you!