Hidde `From<T>` implementations for error types in Rustdoc.

Signed-off-by: Jean Pierre Dudey <jeandudey@hotmail.com>

src/blockdata/script.rs

@@ -195,6 +195,7 @@ impl error::Error for Error {
 }
 
 #[cfg(feature="bitcoinconsensus")]
+#[doc(hidden)]
 impl convert::From<bitcoinconsensus::Error> for Error {
     fn from(err: bitcoinconsensus::Error) -> Error {
         match err {

src/util/mod.rs

@@ -147,18 +147,21 @@ pub fn propagate_err<T>(s: String, res: Result<T, Error>) -> Result<T, Error> {
     res.map_err(|err| Error::Detail(s, Box::new(err)))
 }
 
+#[doc(hidden)]
 impl From<base58::Error> for Error {
     fn from(e: base58::Error) -> Error {
         Error::Base58(e)
     }
 }
 
+#[doc(hidden)]
 impl From<bitcoin_bech32::Error> for Error {
     fn from(e: bitcoin_bech32::Error) -> Error {
         Error::Bech32(e)
     }
 }
 
+#[doc(hidden)]
 impl From<secp256k1::Error> for Error {
     fn from(e: secp256k1::Error) -> Error {
         Error::Secp256k1(e)