libglvnd/mesa3d updates and gl.pc/egl.pc files

Greetings, all, Recently libglvnd was updated to 1.2.0 and mesa3d to 19.2.1. With these versions, the gl.pc and egl.pc files move from mesa3d to libglvnd. Mesa3d drops them IF libglvnd presents them but libglvnd needs to be updated first, causing a conflict. To update properly you'll need to force the libglvnd update (pkgadd -u -f) and then update mesa3d normally. Regards, Matt