Enable strict warnings and fix unused warnings

Test: builds without warnings
Change-Id: I0701a44cbd9a2adc405a1e253b57df7ee03a90b7
diff --git a/media/libeffects/proxy/Android.mk b/media/libeffects/proxy/Android.mk
index 2ba452e..0acf1c0 100644
--- a/media/libeffects/proxy/Android.mk
+++ b/media/libeffects/proxy/Android.mk
@@ -23,6 +23,7 @@
         EffectProxy.cpp
 
 LOCAL_CFLAGS+= -fvisibility=hidden
+LOCAL_CFLAGS += -Wall -Werror
 
 LOCAL_SHARED_LIBRARIES := liblog libcutils libutils libdl libeffects