Add minimal support for building non-GUI parts of wxWidgets for Android.

Recognize __ANDROID__ in wx/platform.h and include the appropriate headers
from wx/android.

Also fix a couple of compilation errors (in filename.cpp) and warnings (in
event.h) which only appear when building for Android.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70703 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/platform.h

@@ -149,6 +149,11 @@
 #   define __WXHANDHELD__
 #endif
 
+#ifdef __ANDROID__
+#   define __WXANDROID__
+#   include "wx/android/config_android.h"
+#endif
+
 /*
    Include wx/setup.h for the Unix platform defines generated by configure and
    the library compilation options