merge mesa 19.1.7 into MesaLib.old.
initial import of Mesa 19.1.7 into MesaLib.old.
spell it defined(__NetBSD__) so it actually matches and we skip this pragma warning during the build: Warning: Per application configuration won't work with your OS version.
import the existing Mesa 10.x sources as MesaLib.old while we handle the upgrade to Mesa 18.x.