pkg-config search path

[Keith Packard]

I'm pretty sure this is the wrong list, but I didn't see a pointer to an 
appropriate list from the pkg-config wiki page :-)

I'm wondering if pkg-config should have a longer default search path for
.pc files; in particular, we're installing quite a few X libaries in /usr/
X11R6 with .pc files in /usr/X11R6/lib/pkgconfig; that leaves everyone who 
uses pkg-config having to set a custom path to locate those files.

I suggest we either hard-code /usr/X11R6/lib/pkgconfig into the pkg-config 
search path or use the system libary path to locate .pc files -- looking 
in ld.so.conf on Linux systems, and wherever necessary on other systems.  
This would make the location of the .pc files follow the location of the 
.so files, which seems like a good idea in some ways.

-keith