- fix page count of postscript files (RHBZ#852410)
- don't treat "no tty" stdin as if there is data to parse there

Trying to read stdin also where it's not a tty causes mysterious errors
when pkpgcounter is run from filters/backends (ex. tea4cups):

Unsupported file format for /var/spool/cups/tmp/tmpXXXXXX (input file /var/spool/cups/tmp/tmpXXXXXX is empty !)

because pkpgcounter tries to parse non-existing input from stdin.
- rel 4