Register delegate to read datas from given buffer

Property definitions

curl $ NativeCurl :: register_read_datas_callback
	# Register delegate to read datas from given buffer
	fun register_read_datas_callback(delegate: NativeCurlCallbacks, datas: String): CURLCode
	do
		if datas.length > 0 then return native_register_read_datas_callback(delegate, datas, datas.length)
		return once new CURLCode.unknown_option
	end
lib/curl/native_curl.nit:187,2--192,4