Finishes external call implementation.

test/libsolidity/semanticTests/array/memory.sol

@@ -0,0 +1,17 @@
+pragma solidity >= 0.6.0;
+
+contract C {
+    function h(uint[4] memory n) public pure returns (uint) {
+        return n[0] + n[1] + n[2] + n[3];
+    }
+
+    function i(uint[4] memory n) public view returns (uint) {
+        return this.h(n) * 2;
+    }
+}
+
+// ====
+// compileViaYul: also
+// ----
+// h(uint256[4]): 1, 2, 3, 4 -> 10
+// i(uint256[4]): 1, 2, 3, 4 -> 20

test/libsolidity/semanticTests/functionCall/external_call.sol

@@ -0,0 +1,17 @@
+pragma solidity >= 0.6.0;
+
+contract C {
+    function g(uint n) external pure returns (uint) {
+        return n + 1;
+    }
+
+    function f(uint n) public view returns (uint) {
+        return this.g(2 * n);
+    }
+}
+
+// ====
+// compileViaYul: also
+// ----
+// g(uint256): 4 -> 5
+// f(uint256): 2 -> 5

test/libsolidity/semanticTests/functionCall/external_call_dynamic_returndata.sol

@@ -0,0 +1,24 @@
+pragma solidity >= 0.6.0;
+
+contract C {
+    function d(uint n) external pure returns (uint[] memory) {
+        uint[] memory data = new uint[](n);
+        for (uint i = 0; i < data.length; ++i)
+            data[i] = i;
+        return data;
+    }
+
+    function dt(uint n) public view returns (uint) {
+        uint[] memory data = this.d(n);
+        uint sum = 0;
+        for (uint i = 0; i < data.length; ++i)
+            sum += data[i];
+        return sum;
+    }
+}
+
+// ====
+// compileViaYul: also
+// EVMVersion: >=byzantium
+// ----
+// dt(uint256): 4 -> 6