update pdnsd and tun2socks to Android-16

add stpcpy function not present before Android-21

jni/Application.mk

@@ -1,4 +1,4 @@
 APP_ABI      			:= armeabi armeabi-v7a arm64-v8a mips x86
-APP_PLATFORM 			:= android-21
+APP_PLATFORM 			:= android-16
 APP_STL      			:= stlport_static
-NDK_TOOLCHAIN_VERSION 	:= 4.9
+NDK_TOOLCHAIN_VERSION 	:= 4.6

jni/pdnsd/src/cache.c

@@ -2697,6 +2697,12 @@ int dump_cache(int fd, const unsigned char *name, int exact)
 	return rv;
 }
 
+char *stpcpy(char *dest, char const *src)
+{
+  strcpy(dest, src);
+  return dest + strlen(dest);
+}
+
 
 #if DEBUG>0