Android: Added config tests for multimedia on android.

The Android multimedia plug-in requires API level 11 to compile, so the
config test will check and issue a message about the requirement if the
API level can't be satisfied.

Change-Id: I6c21fe1255024e853023bd8168dfa917b00c4c23
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

qtmultimedia.pro

@@ -8,6 +8,8 @@ win32 {
     qtCompileTest(evr)
 } else:mac {
     qtCompileTest(avfoundation)
+} else:android {
+    !qtCompileTest(android):error("QtMultimedia for Android requires API level 11")
 } else {
     qtCompileTest(alsa)
     qtCompileTest(pulseaudio)