Use of `strcpy` in these particular cases was safe, but it's hard to
tell and also useless. `strcpy` would effectively need to do another
`strlen` which we already did.
Also removed sprintf, which was also safe in this case but it's easier to
be "obviously safe", especially for static analysers.
"All rights reserved" was incorrect. The project was licensed under GPL3,
which means a lot of rights are licensed to everybody in the world, i.e.
not reserved to the "Tox Project".
It is still C code, so still compatible with C compilers as well. This
change lets us see more clearly where implicit conversions occur by
making them explicit.
bootstrap_node_packets.c was giving an error as it was being included
twice and there were no include guards, so part of it was split into
bootstrap_node_packets.h.
