Create osx_build_script_toxcore.txt

OS X shell script to do everything from git pull to sudo make install for toxcore, after dependencies have already been installed, by MacPorts, from source, etc.
Update INSTALL.md

Added MacPorts related info. to Section heading "OS X Non-homebrew"
Update INSTALL.md
Made toxdns header cpp-friendly
Merge branch 'lyubod-master'
Merge branch 'toxdns-header-fix' of https://github.com/nurupo/InsertProjectNameHere
readme.md: "goals of tox" -> "goals with tox"
Merge branch 'master' of https://github.com/dubslow/toxcore
Merge branch 'patch-3' of https://github.com/stal888/toxcore
Relay peer kill messages too.
Enable IPv6, fix systemd PID bug
Does a realloc with a size of 0 if every port is invalid
Merge branch 'master' of https://github.com/dubslow/toxcore
Merge branch 'master' of https://github.com/stqism/ToxCore
Merge branch 'master' of https://github.com/irungentoo/toxcore
Fix include issue