Log Message:
The configure script defines HAVE_STATVFS as 0 on non-IRIX platforms,
regardless of the result of sys/statvfs.h availability test.  It
results in two definitions of HAVE_STATVFS in confdefs.h.  Check the
availability of sys/statvfs.h only on IRIX platforms to ensure that
HAVE_STATVFS is defined at most once.