Changed pub_nonce_sum and msg_to_sign to be public functions (#557)

* [Dev] changed pub_nonce_sume to be public

* [Dev] made msg_to_sign public to be able to create signatures outside of
slate.rs

Co-authored-by: Jakob <jakob.abfalter@brex.io>

libwallet/src/slate.rs

@@ -379,7 +379,7 @@ impl Slate {
 	}
 
 	// This is the msg that we will sign as part of the tx kernel.
-	fn msg_to_sign(&self) -> Result<secp::Message, Error> {
+	pub fn msg_to_sign(&self) -> Result<secp::Message, Error> {
 		let msg = self.kernel_features()?.kernel_sig_msg()?;
 		Ok(msg)
 	}
@@ -432,7 +432,7 @@ impl Slate {
 	}
 
 	/// Return the sum of public nonces
-	fn pub_nonce_sum(&self, secp: &secp::Secp256k1) -> Result<PublicKey, Error> {
+	pub fn pub_nonce_sum(&self, secp: &secp::Secp256k1) -> Result<PublicKey, Error> {
 		let pub_nonces: Vec<&PublicKey> = self
 			.participant_data
 			.iter()