modesetting: Fix broken manpage in autoconf build
The autoconf build for the modesetting driver still relied on xorg-macros.m4 for string replacements and did not include the top-level manpages.am. As a result, no substitutions took place after commit 2e497bf8. This should be a candidate for the 1.20 branch. Reviewed-by: Michel Dänzer <mdaenzer@redhat.com> (cherry picked from commit de0d39f8)