Add pxtrt::runtimeWarning() support; see https://github.com/Microsoft/pxt/issues/31

libs/microbit/control.ts

@@ -37,4 +37,11 @@ namespace control {
             panic(98)
         }
     }
+
+    /**
+     * Display warning in the simulator.
+     */
+    //% shim=pxtrt::runtimeWarning
+    export function runtimeWarning(message: string) {
+    }
 }

libs/microbit/core.cpp

@@ -316,4 +316,9 @@ namespace pxtrt {
   void* getGlobalsPtr() {
     return globals;
   }
+
+  //%
+  void runtimeWarning(StringData *s) {
+    // noop for now
+  }
 }