ui: fixes for Android 6.0

Use AppCompatTheme and AppCompatActivity where support widgets are used.

Tuleap: #31
Change-Id: Ic73fd8f52ef6acf1a88c70241e152255a3fe3ab4
diff --git a/ring-android/app/src/main/AndroidManifest.xml b/ring-android/app/src/main/AndroidManifest.xml
index 4ba66eb..3bc3fa5 100644
--- a/ring-android/app/src/main/AndroidManifest.xml
+++ b/ring-android/app/src/main/AndroidManifest.xml
@@ -128,7 +128,7 @@
             android:name=".client.CallActivity"
             android:label="@string/app_name"
             android:screenOrientation="portrait"
-            android:theme="@style/AppThemeWithoutOverlay"
+            android:theme="@style/AppThemeWithoutOverlayCompat"
             android:windowSoftInputMode="adjustPan" >
             <intent-filter>
                 <action android:name="android.intent.action.CALL_PRIVILEGED" />