[llvm] Update Developer Policy for copyright notices (PR #123463)

[Chris Lattner via llvm-commits]

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@@ -1154,6 +1154,13 @@ acceptable for their contributions.  We feel that a high burden for relicensing
 is good for the project, because contributors do not have to fear that their
 code will be used in a way with which they disagree.
 
+Embedded Copyright Statements
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lattner wrote:

I'd suggest expanding this a bit, maybe something like "Embedded Copyright or 'Contributed by' Statements"

https://github.com/llvm/llvm-project/pull/123463