proj.android/build_native.sh -> 'to_string' is not a member of 'std'

[IslandPlaya]

I used this when I ran into the same problem…

#if CC_TARGET_PLATFORM == CC_PLATFORM_MAC || CC_TARGET_PLATFORM == CC_PLATFORM_IOS || CC_TARGET_PLATFORM == CC_PLATFORM_ANDROID
template<typename T>
string to_string(const T& t) {
	ostringstream os;
	os << t;
	return os.str();
}
#endif