annotate COPYING @ 32355:4195b84940e9

bdiff: add version to help detect breaking binary changes

Previously, we have no way to detect if a compiled .so file could be used or
not, and blindly load it if it exists. Usually we carefully maintain
compatibility of .so and fallback to pure code gracefully. But if we stick
to the rules, certain nice changes will be impossible to make in a clean
way.

This patch adds a "version" constant to the module so we can detect
inconsistency and take appropriate actions (warn, abort, fallback to pure,
run make automatically) in module loader.

                    GNU GENERAL PUBLIC LICENSE
                       Version 2, June 1991

 Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
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  Ty Coon, President of Vice

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