[SMTChecker] Add support to constructors

test/libsolidity/smtCheckerTests/functions/constructor_simple.sol

@@ -0,0 +1,16 @@
+pragma experimental SMTChecker;
+
+contract C {
+	uint x;
+
+	constructor() public {
+		assert(x == 0);
+		x = 10;
+	}
+
+	function f(uint y) public view {
+		assert(y == x);
+	}
+}
+// ----
+// Warning: (148-162): Assertion violation happens here