libpromises: initialize variable, avoid gcc warning
libcfnet,promises: allow TCP port numbers from 32k-64k

Oddly enough, we had been using "signed short" for TCP port numbers,
limiting usable ports to max 32767. But there are more! I tried to
use the "53308" port and then stumbled upon this limitation.
files_lib.c: cast a const, avoid a gcc warning
server.c: after refusing transfer access, exit the function

Why would we want to continue with the flow and open the file?