LLL: Fix msg macro with six arguments.

The previous macro used the set built-in in a way incompatible with the current
implementation of set. This commit updates the macro to be more transparent in how it's
working and avoids the use of the set and alloc built-ins.

test/liblll/EndToEndTest.cpp

@@ -366,6 +366,23 @@ BOOST_AUTO_TEST_CASE(keccak256_32bytes)
 		fromHex("b10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cf6")));
 }
 
+BOOST_AUTO_TEST_CASE(msg_six_args)
+{
+	char const* sourceCode = R"(
+		(returnlll
+			(seq
+				(when (= 0 (calldatasize))
+					(seq
+						(mstore 0x40 1)
+						(def 'outsize 0x20)
+						(return (msg 1000 (address) 42 0x40 0x20 outsize) outsize)))
+				(when (= 1 (calldataload 0x00))
+					(return (callvalue)))))
+	)";
+	compileAndRun(sourceCode);
+	BOOST_CHECK(callFallbackWithValue(42) == encodeArgs(u256(42)));
+}
+
 BOOST_AUTO_TEST_CASE(create_1_arg)
 {
 	char const* sourceCode = R"(