Split fallback function and introduce "fallback()" and "receive()" syntax.

test/libsolidity/semanticTests/expressions/uncalled_address_transfer_send.sol

@@ -1,5 +1,5 @@
 contract TransferTest {
-	function() external payable {
+	fallback() external payable {
 		// This used to cause an ICE
 		address(this).transfer;
 	}

test/libsolidity/semanticTests/fallback/fallback_or_receive.sol

@@ -0,0 +1,17 @@
+contract C {
+    uint x;
+    uint y;
+    fallback () payable external { ++x; }
+    receive () payable external { ++y; }
+    function f() external returns (uint, uint) { return (x, y); }
+}
+// ----
+// f() -> 0, 0
+// () ->
+// f() -> 0, 1
+// (), 1 ether ->
+// f() -> 0, 2
+// (): 1 ->
+// f() -> 1, 2
+// (), 1 ether: 1 ->
+// f() -> 2, 2

test/libsolidity/semanticTests/fallback/inherited.sol

@@ -0,0 +1,10 @@
+contract A {
+    uint data;
+    fallback() external { data = 1; }
+    function getData() public returns (uint r) { return data; }
+}
+contract B is A {}
+// ----
+// getData() -> 0
+// (): 42 ->
+// getData() -> 1

test/libsolidity/semanticTests/fallback/short_data_calls_fallback.sol

@@ -0,0 +1,17 @@
+contract A {
+    uint public x;
+    // Signature is d88e0b00
+    function fow() public { x = 3; }
+    fallback () external { x = 2; }
+}
+// ----
+// (): hex"d88e0b"
+// x() -> 2
+// (): hex"d88e0b00"
+// x() -> 3
+// (): hex"d88e"
+// x() -> 2
+// (): hex"d88e0b00"
+// x() -> 3
+// (): hex"d8"
+// x() -> 2

test/libsolidity/semanticTests/receive/empty_calldata_calls_receive.sol

@@ -0,0 +1,12 @@
+contract A {
+    uint public x;
+    receive () external payable { ++x; }
+}
+// ----
+// x() -> 0
+// ()
+// x() -> 1
+// (), 1 ether
+// x() -> 2
+// (): hex"00" -> FAILURE
+// (), 1 ether: hex"00" -> FAILURE

test/libsolidity/semanticTests/receive/ether_and_data.sol

@@ -0,0 +1,6 @@
+contract C {
+    receive () payable external { }
+}
+// ----
+// (), 1 ether
+// (), 1 ether: 1 -> FAILURE

test/libsolidity/semanticTests/receive/inherited.sol

@@ -0,0 +1,12 @@
+contract A {
+    uint data;
+    receive() external payable { ++data; }
+    function getData() public returns (uint r) { return data; }
+}
+contract B is A {}
+// ----
+// getData() -> 0
+// () ->
+// getData() -> 1
+// (), 1 ether ->
+// getData() -> 2

test/libsolidity/semanticTests/smoke/fallback.sol

@@ -2,7 +2,7 @@ contract A {
     uint public data;
     uint public balance;
     bytes public externalData;
-    function() external payable {
+    fallback() external payable {
         data += 1;
         balance = msg.value;
         externalData = msg.data;