I don't think you've found what you think you found.
for xserver support of a certain video card, you need
a version of xfree that supports it.
go to www.xfree.org
and try to find stuff about your video
card, and see if a version of xfree supports it.
this will not do you any good, but you can edit the
c file you are messing with and change the the path
to the header file to the exact path where the file
exits on your system. Don't waste your time though.