added missing dependency

jni/libpng-1.5.6/Android.mk

@@ -0,0 +1,23 @@
+LOCAL_PATH:= $(call my-dir)
+
+# libogg
+include $(CLEAR_VARS)
+
+LOCAL_MODULE    := libpng
+LOCAL_CFLAGS    := -fexceptions -g -Dlinux -Dunix \
+	-DHAVE_GCC_DESTRUCTOR=1 -DOPT_GENERIC -DREAL_IS_FLOAT 
+
+LOCAL_CPPFLAGS  := ${LOCAL_CFLAGS}
+
+LOCAL_C_INCLUDES  :=  \
+	${LOCAL_PATH}/include 
+		
+LOCAL_SRC_FILES := \
+	$(filter-out \
+	,$(subst $(LOCAL_PATH)/,,\
+	$(wildcard ${LOCAL_PATH}/*.c) ))
+
+$(info libpng: include dirs $(LOCAL_C_INCLUDES))
+$(info libpng: src files $(LOCAL_SRC_FILES))
+
+include $(BUILD_STATIC_LIBRARY)