@0x/contracts-exchange-libs: Move IWallet from asset-proxy and exchange packages into this package.

contracts/exchange-libs/CHANGELOG.json

@@ -105,6 +105,10 @@
             {
                 "note": "Update `IncompleteFillError` to take an `errorCode`, `expectedAssetFillAmount`, and `actualAssetFillAmount` fields.",
                 "pr": 2075
+            },
+            {
+                "note": "Move `IWallet.sol` from `asset-proxy` and `exchange` packages to here.",
+                "pr": 2233
             }
         ],
         "timestamp": 1570135330

contracts/exchange-libs/contracts/src/IWallet.sol

@@ -0,0 +1,38 @@
+/*
+
+  Copyright 2019 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.5.9;
+pragma experimental ABIEncoderV2;
+
+
+contract IWallet {
+
+    bytes4 internal constant LEGACY_WALLET_MAGIC_VALUE = 0xb0671381;
+
+    /// @dev Validates a hash with the `Wallet` signature type.
+    /// @param hash Message hash that is signed.
+    /// @param signature Proof of signing.
+    /// @return magicValue `bytes4(0xb0671381)` if the signature check succeeds.
+    function isValidSignature(
+        bytes32 hash,
+        bytes calldata signature
+    )
+        external
+        view
+        returns (bytes4 magicValue);
+}