So while working on all various x11 bumps I found out most misc apps does not bother to report proto header files as their dependencies.
As result I decided to place all proto header files to RDEPEND for the respective libraries and be done with it, but if we find any brave soul to run tinderbox checks and report what proto what package needs we could in theory update the deps to be correct.
Why do you need a tinderbox? Just run one of my scripts mentioned in http://www.gentoo.org/proj/en/desktop/x/x11/porting-modular-x-howto.xml. I renamed them to not have the .sh ending and just committed a fix to the doc (linking_libs.sh -> linking_libs and included_headers.sh -> included_headers).
This is really a huge pain for people wanting X on semi-embedded systems like Nokia N900s, etc.
Actualy i just kept the status quo, it was the same way as it was up to now, i tried to remove them from rdepend but failed a bit :)
Also FWIW could you move those scripts to x11 overlay scripts folder? If i remember correctly we decided to not link per-developer webspaces from official guides.