Add special human-readable serde for OutPoint and most bip32 types

[stevenroose]

Serialized OutPoint as "<txid>:<vout>" instead of a struct when a human-readable (de)serializer is used, f.e. JSON.

It should be noted that this is a breaking change for people relying on the current JSON serialization of OutPoint as a struct.

This PR is on top of #269, but doesn't have to be.

Closes #202.

[apoelstra]

This is great. Can you make an analogous PR to rust-elements?

[apoelstra]

I think we should first get rid of the serde macros. They aren't needed since rustc 0.15.

[apoelstra]

Eh, actually there's no reason to get rid of the serde macros yet. ACK mod nit.

[stevenroose]

Eh, actually there's no reason to get rid of the serde macros yet. ACK mod nit.

Were you talking about using derive for the struct macro?

[stevenroose]

I addressed the collect_str comments. This PR merges #269 as well though. If you want to merge this one before that, I guess I could re-push it standalone.

[stevenroose]

Btw, any idea if it's possible to condense that macro in the two other macros? It's kind of a total code duplicate of serde_struct_impl and serde_string_impl with an if-statement to choose which.

[apoelstra]

Yeah, serde_struct_impl could be replaced with #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]. But that's somewhat independent of these changes.

No, I don't have any good ideas about how to reduce code duplication :(

[apoelstra]

utACK

[dongcarl]

I'm not too familiar with serde, but I can attest that:

• The changes in 8d7a1ff isn't more wrong than before
• The changes in ebe6ace9cee3acf9f482f5921f3e4538e80d0bae make sense conceptually
• The changes in 42d3a30dd488e4cddd1aa0fd52c613c4ca78bf4d is correct and doesn't change behavior (or binary output if Rust's "free-abstraction" works)

If anyone can attest to the serde code in ebe6ace9cee3acf9f482f5921f3e4538e80d0bae that'd be great.

[stevenroose]

If anyone can attest to the serde code in ebe6ace that'd be great.

You should be able to see that it's nothing more than the other two serde impl macros combined with an if serializer.human_readable() condition.

[stevenroose]

Fixed Rust v1.22 compilation.

[apoelstra]

re-utACK

[stevenroose]

Added small commit to address @dongcarl 's nit.

[apoelstra]

changes look fine

[dongcarl]

LGTM