Add rust bindings

[lvaccaro]

Use bindgen to add rust bindings at lnsocket C library.

Generate rust bindings and target library with:

make rust

In rust/lib.rs, I open a demo socket connection to my experimental local node.

I am not a rust expert, so I open MR for feedbacks.

NOTE: on arm64 platform, the code failed to compile: it expects a *mut u8 instead *mut i8 on CStr::from_ptr().

[jb55]

awesome, thanks! I had to make a few tweaks to make it work but otherwise LGTM. cherry-picked into b996fb8d1d7a6b578f48ce85fc951450a853bcdf

commit 1d57f518e5b8ff8fd3ce4b328437cdbd59c9bf3d
Author: William Casarin <jb55@jb55.com>
Date:   Thu Jun 30 11:34:43 2022 -0700

    fixup! add rust bindings

diff --git a/Makefile b/Makefile
index 3c656b7..ab7f60c 100644
--- a/Makefile
+++ b/Makefile
@@ -28,8 +28,10 @@ js: target/js/lnsocket.js target/js/lnsocket.wasm

 node: target/node/lnsocket.js target/node/lnsocket.wasm

-rust: lnsocket.a
+liblnsocket.a: lnsocket.a
    cp lnsocket.a liblnsocket.a
+
+rust: liblnsocket.a
    cargo build --release

 target/node/lnsocket.js: target/tmp/node/lnsocket.js lnsocket_lib.js
diff --git a/build.rs b/build.rs
index eaaf8f7..d2e5926 100644
--- a/build.rs
+++ b/build.rs
@@ -22,7 +22,8 @@ fn main() {
         // bindings for.
         .header("lnsocket.h")
         .header("lnsocket_internal.h")
-        .clang_arg("-Ideps/secp256k1/include/")
+        .clang_arg("-Ideps/secp256k1/include")
+        .clang_arg("-Ideps/libsodium/src/libsodium/include")
         .header("deps/secp256k1/include/secp256k1.h")
         .trust_clang_mangling(false)
         // Finish the builder and generate the bindings.

[lvaccaro]

thanks