Implement ABI encoding of calldata arrays and structs.

test/libsolidity/semanticTests/abiEncoderV2/calldata_struct_simple.sol

@@ -0,0 +1,18 @@
+pragma experimental ABIEncoderV2;
+
+contract C {
+    struct S { uint256 a; }
+
+    function f(S calldata s) external returns (bytes memory) {
+        return abi.encode(s);
+    }
+
+    function g(S calldata s) external returns (bytes memory) {
+        return this.f(s);
+    }
+}
+// ====
+// EVMVersion: >homestead
+// ----
+// f((uint256)): 3 -> 32, 32, 3
+// g((uint256)): 3 -> 32, 32, 3