Remove some immediatly overwritten writes

Fix local variable being modified just before it goes out of scope

When memcpy-ing in a buffer, only memset the part of the buffer not modified by the memcpy, not the whole buffer

Also reorder the memset after the memcpy, to potentially avoid cache misses (NOT profiled)
Fix exceptional file leak in other/fun/sign.c
Fix redundant assignment in TCP_server.c
Merge branch 'mannol1-master'
Merge branch 'perf-rebase' of https://github.com/tux3/toxcore
Merge branch 'leak-rebase' of https://github.com/tux3/toxcore
Merge branch 'tcpserv' of https://github.com/tux3/toxcore
Fix CppCheck style errors

#if 0 the content of toxav/msi.c : int stringify_message(MSIMessage
*msg, char *dest)
This function has no effect and does not seem to be used for actively
waiting.

Fix various other style errors, reduce scope when possible, avoid
redundant writes, clarify operator priorities, etc.
Got a little dated
Fix FreeBSD instructions, sodium 0.5.0

Sodium 0.5.0 optimizes itself on being loaded
Update README.md
Merge branch 'tux3-cppcheck-style'
Merge branch 'patch-1' of https://github.com/stqism/ToxCore
Merged upstream