We are not using make, we're using gnu make. Make sure that OpenBSD
knows this.
Add Net, Free, and Dragonfly BSDs in the gmake dance.
fix spelling for clean-internals
Merge pull request #344 from cgzones/spelling

fix spelling for clean-internals
Reminded by @cgzones that this needs to be set for non-BSD systems
as well.
Merge pull request #343 from ddpbsd/makefile-fallout

gnu make fallout
fix several -Wextra warnings