Provide static feature

[el7cosmos]

Description

Resolves #549

Checklist

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• I have added tests that prove my code works as expected.
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[coveralls]

Pull Request Test Coverage Report for Build 18747403298

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 27.709%

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Totals
Change from base Build 18634693923:	0.0%
Covered Lines:	1156
Relevant Lines:	4172

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💛 - Coveralls

[ptondereau]

thanks for this PR!

Mind you, if you can add some docs, even a one-phraser to show features and the usage?

[el7cosmos]

I've added some docs in README, does that make sense?

Also note that since bindgen/runtime and bindgen/static are mutually exclusive, we can't use --all-features. I've changed --all-features usage in various places in this repo, but, if there is any new feature introduced in the future, that will need to be added explicitly