Updated version checks for PHP 5

Ignore-this: 97d3d6fd8dc65d0cfce6b976cc2fad28

The next release will require PHP 5, the related checks were upgraded to check
for at least 5.0.0 (we might need to tune this)

darcs-hash:20090726115255-7ad00-59d67b61739db8eea0288a8010d7cdf507ab867b.gz