Use a bundled protocol definition struct

This is necessary for the X server to build if the protocol headers are
old, so that I can get testing on the CI.
5 jobs for extended-shm in 4 minutes and 20 seconds (queued for 8 seconds)
latest
Status Name Job ID Coverage
  Docker Image
passed debian-buster #13187944

00:00:10

 
  Build And Test
passed autotools #13187945

00:04:10

passed meson #13187946

00:01:38

passed meson-noglamor #13187947

00:01:21

passed mingw-cross-build #13187948

00:00:31