[yul-phaser] Program: Output operator for ErrorList

- It does not seem universal enough to put it in liblangutil but in the scope of yul-phaser it's generic enough so I'm going to keep it together with Program.

tools/yulPhaser/Program.h

@@ -41,6 +41,13 @@ struct Dialect;
 
 }
 
+namespace std
+{
+
+std::ostream& operator<<(std::ostream& _outputStream, solidity::langutil::ErrorList const& _errors);
+
+}
+
 namespace solidity::phaser
 {