Upgrade solc version to 0.5.3 for exchange-libs and utils

contracts/utils/contracts/src/LibAddressArray.sol

@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.3;
 
 import "./LibBytes.sol";
 
@@ -31,7 +31,7 @@ library LibAddressArray {
     /// @return Array of addresses: [... addressArray, addressToAppend]
     function append(address[] memory addressArray, address addressToAppend) 
         internal pure
-        returns (address[])
+        returns (address[] memory)
     {
         // Get stats on address array and free memory
         uint256 freeMemPtr = 0;

contracts/utils/contracts/src/LibBytes.sol

@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.3;
 
 
 library LibBytes {

contracts/utils/contracts/src/Ownable.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.3;
 
 import "./interfaces/IOwnable.sol";
 

contracts/utils/contracts/src/ReentrancyGuard.sol

@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.3;
 
 
 contract ReentrancyGuard {

contracts/utils/contracts/src/SafeMath.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.3;
 
 
 contract SafeMath {

contracts/utils/contracts/src/interfaces/IOwnable.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.3;
 
 
 contract IOwnable {

contracts/utils/contracts/test/TestConstants.sol

@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.3;
 
 import "../src/LibBytes.sol";
 

contracts/utils/contracts/test/TestLibBytes.sol

@@ -16,7 +16,7 @@
 
 */
 
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.3;
 
 import "../src/LibBytes.sol";
 
@@ -244,14 +244,14 @@ contract TestLibBytes {
     /// @param length Length of bytes to copy from <source> to <dest>
     /// @return mem Memory contents after calling memCopy.
     function testMemcpy(
-        bytes mem,
+        bytes memory mem,
         uint256 dest,
         uint256 source,
         uint256 length
     )
         public // not external, we need input in memory
         pure
-        returns (bytes)
+        returns (bytes memory)
     {
         // Sanity check. Overflows are not checked.
         require(source + length <= mem.length);