After upgrading to media-libs/mesa-9.2.0-r1, the Gallium versions of drivers are no longer installed. Build log attached.
Created attachment 359210 [details] build.log.gz
Please don't panic, the packages are p.masked now, and I'm starting to build them to find the issue.
The driver renaming code in ebuild used ${S} incorrectly. It should be fixed now, both in gx86 version and in the x11 repository. Thanks for the report.