Update the secp256k1-sys codebase to version v0.6.

[jlest01]

This PR updates the secp256k1-sys codebase to version v0.6.
I'm not sure if there are more steps involved, but these commits work fine in #716.

[apoelstra]

Thanks for doing this! Before running the vendor script, can you update the version in secp256k1-sys/Cargo.toml from 0.10.0 to 0.11.0? We need to update the version in order to make this releaseable, and because our vendoring code embeds the full version into all the symbols, and changing the name of these symbols is a breaking change, we don't have the ability to do minor bumps.

Could you also add an initial commit to this PR which edits secp256k1-sys/vendor-libsecp.sh to remove the patch version from DEFAULT_VERSION_CODE? I think adding | cut -d_ -f1-2 to the current command that computes it will do this.

I don't know why I didn't think to do this years ago..

[jlest01]

@apoelstra thanks. I added two new initial commits.

[apoelstra]

Can you also update the Cargo-recent.lock and Cargo-minimal.lock files in the repo?

[apoelstra]

That should get CI passing -- then I can test the last commit and ACK it -- and then I'll ask you to squash everything, even though your change are logically separate and nicely separated. Because unfortunately none of the changes work without the others.

[jlest01]

@apoelstra done. Thanks

[jlest01]

I had squashed everything, but then I realized you asked to do it after the review.
Cargo-recent.lock and Cargo-minimal.lock were changed in d88e6c2

[apoelstra]

utACK 0cdc758a56360bf58a851fe91085a327ec97685a

Thanks for iterating!!

If you squash everything I can do a tested ACK and merge it. (I already tested the tip so it will pass after squashing.)

[apoelstra]

Err, utack 32a533c I mean. Copied the wrong commit.

[jlest01]

Thanks for reviewing. All commits squashed.

[apoelstra]

ACK 06ab8d0; successfully ran local tests; thanks for iterating!