Add /proc/version for procfs with -o linux. The version reported depends
on the emulation type of the calling process:
$ cat /proc/version
NetBSD version 5.99.55 (netbsd@localhost) (gcc version 4.1.3 20080704 prerelease (NetBSD nb2 20081120)) NetBSD 5.99.55 (GENERIC) #39: Sun Sep 4 09:10:05 EDT 2011
$ /emul/linux/bin/cat /proc/version
Linux version 2.6.18 (linux@localhost) (gcc version 4.1.3 20080704 prerelease (NetBSD nb2 20081120)) #0 Wed Mar 3 03:03:03 PST 2010
$ /emul/linux32/bin/cat /proc/version
Linux version 2.6.18 (linux32@localhost) (gcc version 4.1.3 20080704 prerelease (NetBSD nb2 20081120)) #0 Wed Mar 3 03:03:03 PST 2010