xorgproto header installation conflicts

[Thomas Klausner]

Hi!

I've updated pkgsrc to use xorgproto 2019.2, still installing the
legacy headers with --enable-legacy, and we had to fix a couple
conflicts:

* XKBgeom.h is provided by libX11 1.6.9
* vlcXvMC.h is provided by libXvMC 1.0.12

I guess as long as they are installed by the other libraries, they
should not be installed by xorgproto. Or should they be removed from
the other libraries?
 Thomas