freeglut: migrate to core
freeglut: migrate to core

Closes #272

Signed-off-by: Bob W. Hogg <c772a964fd55352a3510e5d535dd9ccc9ac30168@linux.com>
LinuxbrewTestBot/homebrew-xorg,Linuxbrew/homebrew-xorg,maxim-belkin/homebrew-xorg