Eliminate warnings, add -Wall and -Werror to all projects.

This change enables all warnings and treats warnings as errors. As
a result, nobody should be able to submit new code to bluedroid
that contains compiler warnings. Instead, they should fix the warnings
before submitting.

This change has already caught a type mismatch bug in
stack/avrc/avrc_api.c where an integer was being stored in a boolean.

Change-Id: Ic41960754b39a1a6aa37f1c1095003195f466183
diff --git a/gki/Android.mk b/gki/Android.mk
index d00478d..116664b 100644
--- a/gki/Android.mk
+++ b/gki/Android.mk
@@ -9,7 +9,7 @@
                    $(LOCAL_PATH)/../utils/include \
                    $(bdroid_C_INCLUDES) \
 
-LOCAL_CFLAGS += -Werror -Wno-error=unused-parameter $(bdroid_CFLAGS) -std=c99
+LOCAL_CFLAGS += -Wno-error=unused-parameter $(bdroid_CFLAGS) -std=c99
 
 ifeq ($(BOARD_HAVE_BLUETOOTH_BCM),true)
 LOCAL_CFLAGS += \