add app engine core lib for testing

this allows these classes to be included for native testing

Author: diegomarquezp

google-http-client-appengine/pom.xml

@@ -72,6 +72,12 @@
     <dependency>
       <groupId>com.google.appengine</groupId>
       <artifactId>appengine-api-1.0-sdk</artifactId>
+      <scope>provided</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.google.appengine</groupId>
+      <artifactId>appengine-api-1.0-sdk</artifactId>
+      <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>com.google.appengine</groupId>