Restrict max code size to 23999 bytes for EIP-150 and after.

json/src/spec/ethash.rs

@@ -92,6 +92,11 @@ pub struct EthashParams {
 	/// See main EthashParams docs.
 	#[serde(rename="ecip1010ContinueTransition")]
 	pub ecip1010_continue_transition: Option<Uint>,
+
+	/// See main EthashParams docs.
+	#[serde(rename="maxCodeSize")]
+	pub max_code_size: Option<Uint>,
+
 }
 
 /// Ethash engine deserialization.