Add a feature to disable replacing C symbols with rust

[elichai]

Hi,
Requested in IRC by @TheBlueMatt the main use case is bitcoin core integration.
such that you can use upstream's libsecp256k1 with this library.

this feature is not compatible with no-std.

[apoelstra]

Can you put a // Do not use this feature! or something warning that this is a bad/unsupported thing and we are only doing it for Core's sake, because Core shares developers with both this project and upstream libsecp?

[elichai]

Done. took the liberty and added that warning to fuzztarget too.
(FYI #154 )

[TheBlueMatt]

ACK. This 176 appears to fully solve my issues linking into Core with its libsecp.

[apoelstra]

I like the comment. Matt's ACK is good enough for me.

[stevenroose]

@elichai @TheBlueMatt so are you saying that you are using the C symbols exported by rust-secp? I don't think that's what this crate is supposed for, is it?

Doing that would also stop working with #169, which arguably makes this crate more interoperable with other systems.

[stevenroose]

Oh I think I understood it wrong. You're using this library with the libsecp symbols already exported in Core?

That already makes more sense to me, but I think that will still be hard to make work with #169.

[TheBlueMatt]

Right, for #169 we’ll need a feature to skip the -sys dependency and not use version-tagged symbols.

…

On Oct 29, 2019, at 02:46, Steven Roose ***@***.***> wrote:  Oh I think I understood it wrong. You're using this library with the libsecp symbols already exported in Core? That already makes more sense to me, but I think that will still be hard to make work with #169. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or unsubscribe.