Always skip the /proc filesystem

     Change: always-skip-proc-filesystem
     Purpose: Always skip the /proc filesystem
     Reason: OpenPKG never does anything with the virtual filesystem
                     /proc which exists on some platforms. Sometimes
                     (e.g. in a FreeBSD Jail) the problem even exists
                     that RPM discovers that /proc might be available
                     (because the FreeBSD host leaks this information
                     to the Jail) but /proc cannot be actually accessed
                     from within the Jail. As a result, RPM complains
                     with "error: failed to stat /proc: No such file
                     or directory" all the time.. As OpenPKG never
                     fiddles around with /proc from within RPM, in this
                     particular vendor environment /proc safely can be
                     just ignored.