vncpcap2john: add license blurb for own contribs
Makefile: add proper dependency information for vncpcap2john
vncpcap2john: remove bogus NUL check in makehex()

the data is binary, not a zero-terminated string, so it can contain NULs.
Merge pull request #534 from rofl0r/vnclicense

vncpcap license update
Various signal.c tweaks for MPI: Avoid signal loops when signaling
parent for reload. If running Cygwin w/ fork or MPI, save session on
key press in case a following termination does not save properly.
Also clarify MPI requirements in doc/README-mpi.