make all libsurfaceflinger and libsensorservice symbols's visibility hidden

we only export the main entry-point.
this saves about 150KB.

Change-Id: I55eb2b6705386fdfa43860deb62f9cdd2a0982aa
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 66c2d42..e7745b8 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -79,11 +79,11 @@
                        private HWComposer::EventHandler
 {
 public:
-    static char const* getServiceName() {
+    static char const* getServiceName() ANDROID_API {
         return "SurfaceFlinger";
     }
 
-    SurfaceFlinger();
+    SurfaceFlinger() ANDROID_API;
 
     enum {
         EVENT_VSYNC = HWC_EVENT_VSYNC