Size issue

[pauleffect90]

https://github.com/php-ion/websocket-parser/blob/6f506c6f2cbb88607e79c02d6277c2f48c840047/websocket_parser.c#L227

On 32bit systems (most MCUs out there), size_t is usually 32bits wide. The referenced code could produce unexpected results. I suggest explicitly setting the variable's [data_len] length to 64bits wide.