Remove pciutils support

These three commits remove pciutils support, per #100.  Things to note / things I'd like feedback on before bringing to the main upstream hwloc repo:

1. Make sure I got everything / removed all pciutils support without damaging libpciaccess support.
1. If libpciaccess isn't found via pkg-config, I put in a check for pciaccess.h and libpciaccess the old fashioned way (AC_CHECK_HEADER / AC_CHECK_LIB).  I have a dim recollection that we *used* to have this, but took it out... but I can't think of why we would have done that.  Am I forgetting something?

Motivation for the 2nd bullet is because RHEL has libpciaccess, but it does not have a pkg-config .pc file for them, so my system consistently does not build libpciaccess support.