make libaudioflinger symbols visibility hidden

we export only symbols needed by clients of this library.
this saves about 130KB (1/3rd of the lib size)

Change-Id: Id81f3ecb299ee3abc0811915cf6efe87180bf15c
diff --git a/services/audioflinger/AudioPolicyService.h b/services/audioflinger/AudioPolicyService.h
index 35cf368..53238fa 100644
--- a/services/audioflinger/AudioPolicyService.h
+++ b/services/audioflinger/AudioPolicyService.h
@@ -19,6 +19,7 @@
 
 #include <cutils/misc.h>
 #include <cutils/config_utils.h>
+#include <cutils/compiler.h>
 #include <utils/String8.h>
 #include <utils/Vector.h>
 #include <utils/SortedVector.h>
@@ -44,7 +45,7 @@
 
 public:
     // for BinderService
-    static const char *getServiceName() { return "media.audio_policy"; }
+    static const char *getServiceName() ANDROID_API { return "media.audio_policy"; }
 
     virtual status_t    dump(int fd, const Vector<String16>& args);
 
@@ -137,7 +138,7 @@
     virtual status_t setVoiceVolume(float volume, int delayMs = 0);
 
 private:
-                        AudioPolicyService();
+                        AudioPolicyService() ANDROID_API;
     virtual             ~AudioPolicyService();
 
             status_t dumpInternals(int fd);