Android: Re-enable threaded rendering

In Qt 5.2.x, the platform plugin inherited from the EGLFS platform
plugin, so calling the super class implementation of hasCapability()
would return true for ThreadedOpenGL. Since this link was removed
in Qt 5.3, we would return false for all devices, giving us a large
performance regression.

Task-number: QTBUG-37586
Change-Id: I27758649ee9c0921902787b93be943751c839eb8
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>
Reviewed-by: BogDan Vatra <bogdan@kde.org>
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>

src/plugins/platforms/android/qandroidplatformintegration.cpp

@@ -152,7 +152,8 @@ bool QAndroidPlatformIntegration::hasCapability(Capability cap) const
         case ThreadedOpenGL:
             if (needsWorkaround())
                 return false;
-        // fall through
+            else
+                return true;
         default:
             return QPlatformIntegration::hasCapability(cap);
     }