Make Map trait private to psbt module

The `Map` trait has been deemed confusing and not that useful to users
of the library, we still use it internally within the `psbt` module
though so make it visible only in `psbt` and `psbt::map`.

src/util/psbt/map/mod.rs

@@ -28,7 +28,7 @@ pub use self::input::{Input, PsbtSigHashType};
 pub use self::output::{Output, TapTree};
 
 /// A trait that describes a PSBT key-value map.
-pub trait Map {
+pub(super) trait Map {
     /// Attempt to insert a key-value pair.
     fn insert_pair(&mut self, pair: raw::Pair) -> Result<(), encode::Error>;
 

src/util/psbt/mod.rs

@@ -39,7 +39,8 @@ mod macros;
 pub mod serialize;
 
 mod map;
-pub use self::map::{Map, Input, Output, TapTree};
+pub use self::map::{Input, Output, TapTree};
+use self::map::Map;
 
 use util::bip32::{ExtendedPubKey, KeySource};