Import source to librtti

Summary:

- Import initial source

Test Plan:
NA

src/str.c

@@ -0,0 +1,23 @@
+#include <errno.h>
+#include <stdlib.h>
+
+#include "rtti.h"
+
+char* toString(var v, ...)
+{
+    to_string_fn_t method = NULL;
+    va_list        ap;
+    char*          s = NULL;
+
+    RTTI_GET_METHOD(method, v, toString, toString);
+    if (method == NULL) {
+        errno = -EINVAL;
+        return NULL;
+    }
+
+    va_start(ap, v);
+    s = method(v, ap);
+    va_end(ap);
+
+    return s;
+}