move struct req declaration up avoid a dummy `struct req;'

re-align declarations

reorder

drop req_by_id_req, allow req_by_id to return NULL

drop setup_tls

wrap some long lines

deallocate memory before exiting it's not really required, we're gonna quit anyway, but it's cleaner and helps reducing the clutter when using leak detection tools.

refactor net code Generalize a bit the flow. Expect a request to be written and a body to be sended with net_send_ui. This will make easier to add other protocols like finger or gopher in the future. Also, switch to evbuffer instead of manually calling tls_read/write: with evbuffers we can abstract over the actual I/O routine and just read/write buffers in memory. This too will help with adding more protocols.

rename client -> net

rename gemini.c -> net.c