Preliminary strings

While not well-wrought, it's at least possible now to log some stuff when debugging

tests/compiler/std/string.ts

@@ -0,0 +1,18 @@
+// preliminary
+
+var str: string = "hi, I'm a string";
+
+// exactly once in static memory
+assert(changetype<usize>(str) === changetype<usize>("hi, I'm a string"));
+
+assert(str.length == 16);
+assert(str.charCodeAt(0) == 0x68);
+assert(str.startsWith("hi"));
+assert(str.endsWith("string"));
+assert(str.includes("I'm"));
+assert(str.indexOf(",") == 2);
+assert(str.indexOf("x") == -1);
+
+export function getString(): string {
+  return str;
+}