clean up FreeBSD pci methods and incorporate local patches

This is a fairly big merge request, that cleans up the FreeBSD libpciaccess methods, and incorporates local patches we've had in our ports tree for ages, as well as add some new functionality. I have tried to separate white space changes, since our local patches had a bunch of those, and incorporating those as well made it easier to push everything. Our local patches add support for legacy I/O methods for new architectures, using ioctl()s rather than inb/outb, and tries to fix things for sparc64.

New stuff not previously in the FreeBSD ports tree: I've cleaned up so that we no longer support old versions of FreeBSD, but a the same time, this makes the code easier to read through. This includes getting rid of the autoconf check for pci_io.pi_sel.pc_domain, pc_domain has been part of this struct for a long time. I also removed the old probe methods that didn't use the PCIOCGETBAR ioctl, which has been part of FreeBSD for 10 years. I've also added a new method for has_kernel_driver, using the PCIOCATTACHED ioctl().

This is a fairly big change, and perhaps should have been broken in several merge requests, however the changes build on each other, making it hard to separate.