Adds CGO build flags for freebsd.
This address issued #119
Merge pull request #120 from jteeuwen/master

Adds build flags for freebsd.
added function to do instancing
Merge pull request #123 from krux02/master

added function to do instancing
Added glPrimitiveRestartIndex()
Merge pull request #124 from pakanek/primRestartIndex

Added glPrimitiveRestartIndex()