Reduce the scope of bytes_read in read_pop_response_sync()

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>
Pass buf to read_pop_response_sync() as a char *

Previously we were passing the buf variable into read_pop_response_sync
as void *, however in the read(2) syscall we are doing some pointer
arithamtic on buf and pointer arithmatic on void * is undefined.

Seeing as buf is defined as a char [] just pass it in as a char *

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>
Remove an unused variable assignment in do_connect()

We don't do anything when reading in the response from sending the
username.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>