How to check for some Xorg server features at build time

[Juergen Beisert]

Hi all,

currently I'm trying to write a graphics driver for my hardware. 
The "configure" step of each hardware driver checks for various features, 
header files and so on. As I read them this questiones come into my mind:
- Do I have to check for all features the Xorg server supports and also
  include at buildtime only those features in my driver that are also present
  in the server? For example DGA or DPMS. There are switches to disable these
  features at build time in the server. What happens if my driver tries to use
  these features at runtime?
- If I want to follow the server and if a specific feature is disabled in the
  server I also want to disable this feature (=not compile) in my driver? Are
  there standard macros for the autotools to check for various features if
  they enabled or not in the server I can use in my "configure.ac" script?

Regards,
Juergen