use getApplicationContext() when storing a passed in Context

getApplicationContext() returns the Context of the application, which is
guaranteed to have the same life as the app itself.  Other Contexts, like
an Activity, might go away during runtime.

src/org/fdroid/fdroid/localrepo/LocalRepoManager.java

@@ -73,7 +73,7 @@ public class LocalRepoManager {
     }
 
     private LocalRepoManager(Context c) {
-        context = c;
+        context = c.getApplicationContext();
         pm = c.getPackageManager();
         assetManager = c.getAssets();
         prefs = PreferenceManager.getDefaultSharedPreferences(c);

src/org/fdroid/fdroid/net/LocalHTTPD.java

@@ -27,7 +27,7 @@ public class LocalHTTPD extends NanoHTTPD {
         super(FDroidApp.ipAddressString, FDroidApp.port);
         this.logRequests = false;
         this.webRoot = webRoot;
-        this.context = context;
+        this.context = context.getApplicationContext();
         if (useHttps)
             enableHTTPS();
     }