moved ERC165 interface IDs from ERC721 implementation files to the interface file (#1070)

contracts/token/ERC721/ERC721Basic.sol

@@ -8,6 +8,43 @@ import "../../introspection/ERC165.sol";
  * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
  */
 contract ERC721Basic is ERC165 {
+
+  bytes4 internal constant InterfaceId_ERC721 = 0x80ac58cd;
+  /*
+   * 0x80ac58cd ===
+   *   bytes4(keccak256('balanceOf(address)')) ^
+   *   bytes4(keccak256('ownerOf(uint256)')) ^
+   *   bytes4(keccak256('approve(address,uint256)')) ^
+   *   bytes4(keccak256('getApproved(uint256)')) ^
+   *   bytes4(keccak256('setApprovalForAll(address,bool)')) ^
+   *   bytes4(keccak256('isApprovedForAll(address,address)')) ^
+   *   bytes4(keccak256('transferFrom(address,address,uint256)')) ^
+   *   bytes4(keccak256('safeTransferFrom(address,address,uint256)')) ^
+   *   bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)'))
+   */
+
+  bytes4 internal constant InterfaceId_ERC721Exists = 0x4f558e79;
+  /*
+   * 0x4f558e79 ===
+   *   bytes4(keccak256('exists(uint256)'))
+   */
+
+  bytes4 internal constant InterfaceId_ERC721Enumerable = 0x780e9d63;
+  /**
+   * 0x780e9d63 ===
+   *   bytes4(keccak256('totalSupply()')) ^
+   *   bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) ^
+   *   bytes4(keccak256('tokenByIndex(uint256)'))
+   */
+
+  bytes4 internal constant InterfaceId_ERC721Metadata = 0x5b5e139f;
+  /**
+   * 0x5b5e139f ===
+   *   bytes4(keccak256('name()')) ^
+   *   bytes4(keccak256('symbol()')) ^
+   *   bytes4(keccak256('tokenURI(uint256)'))
+   */
+
   event Transfer(
     address indexed _from,
     address indexed _to,

contracts/token/ERC721/ERC721BasicToken.sol

@@ -13,26 +13,6 @@ import "../../introspection/SupportsInterfaceWithLookup.sol";
  */
 contract ERC721BasicToken is SupportsInterfaceWithLookup, ERC721Basic {
 
-  bytes4 private constant InterfaceId_ERC721 = 0x80ac58cd;
-  /*
-   * 0x80ac58cd ===
-   *   bytes4(keccak256('balanceOf(address)')) ^
-   *   bytes4(keccak256('ownerOf(uint256)')) ^
-   *   bytes4(keccak256('approve(address,uint256)')) ^
-   *   bytes4(keccak256('getApproved(uint256)')) ^
-   *   bytes4(keccak256('setApprovalForAll(address,bool)')) ^
-   *   bytes4(keccak256('isApprovedForAll(address,address)')) ^
-   *   bytes4(keccak256('transferFrom(address,address,uint256)')) ^
-   *   bytes4(keccak256('safeTransferFrom(address,address,uint256)')) ^
-   *   bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)'))
-   */
-
-  bytes4 private constant InterfaceId_ERC721Exists = 0x4f558e79;
-  /*
-   * 0x4f558e79 ===
-   *   bytes4(keccak256('exists(uint256)'))
-   */
-
   using SafeMath for uint256;
   using AddressUtils for address;
 

contracts/token/ERC721/ERC721Token.sol

@@ -13,22 +13,6 @@ import "../../introspection/SupportsInterfaceWithLookup.sol";
  */
 contract ERC721Token is SupportsInterfaceWithLookup, ERC721BasicToken, ERC721 {
 
-  bytes4 private constant InterfaceId_ERC721Enumerable = 0x780e9d63;
-  /**
-   * 0x780e9d63 ===
-   *   bytes4(keccak256('totalSupply()')) ^
-   *   bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) ^
-   *   bytes4(keccak256('tokenByIndex(uint256)'))
-   */
-
-  bytes4 private constant InterfaceId_ERC721Metadata = 0x5b5e139f;
-  /**
-   * 0x5b5e139f ===
-   *   bytes4(keccak256('name()')) ^
-   *   bytes4(keccak256('symbol()')) ^
-   *   bytes4(keccak256('tokenURI(uint256)'))
-   */
-
   // Token name
   string internal name_;