devLibPCI prototype

["Davidsaver, Michael" <mdavidsaver@bnl.gov>]

I have posted a branch to launchpad with a prototype for the PCI
extension to devlib.  It has been tested with rtems 4.9.2 on an
mvme3100.

https://code.launchpad.net/~mdavidsaver/epics-base/devlib

It adds the following changes

1) The VME access functions are moved to devLibVME.h.  The error codes
and some misc macros remain in devLib.h.

2) Remove unimplemented old PCI api

3) Adds devLibPCI.h

At the moment the only implementation is RTEMS.  However, given the
similarity between the two apis (pci_find_device vs. pciFindDevice) they
could probably even share an implementation.

Aside from renaming devLib.h to devLibVME.h no changes are made to the
existing VME api.  However, the unimplemented PCI functions are removed.
I have left the ISA functions in since they are implemented.

4) Adds epicsMMIO.h

Given the lack of uniformity this is really a statement of intent.
Also, using a consistent set of macro/function names will make porting
device support to new targets easier.