Added more tests

tests/programs/len.q

@@ -0,0 +1,14 @@
+import mem
+
+main() {
+	a := mem.alloc(16)
+	assert len(a) == 16
+	mem.free(a)
+
+	assert len("H") == 1
+	assert len("He") == 2
+	assert len("Hel") == 3
+	assert len("Hell") == 4
+	assert len("Hello") == 5
+	assert len("日本") == 6
+}