added field 'onion_request *' to 'pwrite' request

[Konstantin9403]

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[davidmoreno]

Hi,

sorry to check this pull request so late, but, can you provide a description here about whats the end goal of adding this feature?

Also, I would prefer that instead of returning the function that does the job (listen_point.c:101), it calls the function, as it does with onion_low_malloc and onion_low_free. (low.c)