sane darshan integration
Currently, we use an svn revision of darshan that:
- doesn't provide version info into it's .pc file
- requires patching the .pc to provide an include to a build header that's not installed
We should check newer versions of darshan and pick one that has these issues fixed and that we can run the old log formats under.
After that's figured out, remove the --with-darshan option and go solely through pkg-config + version checks.