[SMTChecker] Support array length

test/libsolidity/smtCheckerTests/array_members/length_function_call.sol

@@ -0,0 +1,10 @@
+pragma experimental SMTChecker;
+
+contract C {
+	uint[] arr;
+	function f() public view {
+		assert(arr.length == g().length);
+	}
+	function g() internal pure returns (uint[] memory) {
+	}
+}