osrelease.sh

[Jeff Rizzo <riz%netbsd.org@localhost>]

sys/conf/osrelease.sh underwent some editing back in November 2009 to 
fix PR/42321, and in the process, its behavior with respect to 
non-numeric version numbers changed... which I didn't notice until we 
had one. :)   6.0_BETA is displayed as "6.0", which I think is not quite 
what we want - but I'm not certain the most appropriate fix.

Thoughts?

+j