Partition fixes for probepart and puppyinstaller

A couple of problems were identified with recognising partitions, and npierce and Karl Godt have both posted fixes:
http://www.murga-linux.com/puppy/viewtopic.php?t=85965

I have implemented both of those fixes. That's great, thanks!

Woof commit:
http://bkhome.org/fossil/woof2.cgi/info/c4c40a95c6

Tags: woof