Delegate to inner type for encode_format

In the ToSql impls for &T and Option<T>, override encode_format to
delegate to the impl for T. This ensures that if T overrides this
method, it also overrides it for &T and Option<T>.

postgres-types/src/lib.rs

@@ -868,6 +868,10 @@ where
         T::accepts(ty)
     }
 
+    fn encode_format(&self) -> Format {
+        (*self).encode_format()
+    }
+
     to_sql_checked!();
 }
 
@@ -887,6 +891,13 @@ impl<T: ToSql> ToSql for Option<T> {
         <T as ToSql>::accepts(ty)
     }
 
+    fn encode_format(&self) -> Format {
+        match self {
+            Some(ref val) => val.encode_format(),
+            None => Format::Binary,
+        }
+    }
+
     to_sql_checked!();
 }