way to detect to xserver-xorg version

[Tias]

Hey,

In my program, I want to check that the xserver-xorg version is >= 
1.8.0. What way to do this is advised:

At runtime using XVendorRelease(), or do there exist different releases 
with inconsistent numbering ? And should this be combined with a literal 
match on XServerVendor() ?

At configuration time, PKG_CHECK_MODULES(XSERVER18, [xorg-server >= 
1.8.0], FOO=bar, FOO=baz). But what if you want to discriminate 
different versions, multiple PKG_CHECK_MODULES ? This would swamp the 
number of _LIBS and _CFLAGS options...
Also, PKG_CHECK_EXSISTS() seems to ignore the version I provided, and 
always sets FOO=bar.


Thanks,
Tias