Added sysfs support

Added sysfs support

* lib/pci.h (PCIADDR_PORT_FMT): Use %llx instead of %Lx, because the latter
is not supported by all C libraries.

* Makefile: Always enter the lib directory (remember that we don't have
full dependecies for the library in the top-level Makefile; hmmm, another
thing to rewrite some day).

* lib/sysfs.c: Added Linux sysfs access method based on the patch
written by Matthew Wilcox <willy@fc.hp.com>.

* lib/proc.c: Renamed the access method name from "/proc/bus/pci" to "Linux-proc".

* lib/pread.h: The hacks to support pread on various versions
of Linux libc moved there.

* lib/proc.c (proc_setup): The return value of snprintf() varies
between glibc versions, so we need to check both for a negative
values and for too large values.
git-archimport-id: mj@ucw.cz--public/pciutils--main--2.2--patch-33