fixes for solc-0.5.x

examples/solidity/basic/constants.sol

@@ -1,5 +1,3 @@
-pragma solidity ^0.4.24;
-
 contract Constants {
   bool found = false;
 
@@ -8,11 +6,11 @@ contract Constants {
   }
 
   function find2(address a) public {
-    if (a == 0x123) {found = true;}
+    if (a == address(0x123)) {found = true;}
   }
 
-  function find3(string s) public {
-    if (keccak256(s) == keccak256("test")) {found = true;}
+  function find3(string memory s) public {
+    if (keccak256(bytes(s)) == keccak256("test")) {found = true;}
   }
 
   function echidna_found() public view returns (bool) {