memory stick the easy way

I got tired of having to jump through hoops to install NetBSD on my
Eee PC, so I wrote a simple script to take a NetBSD release ISO and
convert it to an image that can be written to a USB memory stick.

To use the script, simply feed it an ISO and tell it where to write
the resulting image:

# sh mkmemstick.sh i386cd-5.0.1.iso i386memstick-5.0.1.img

The resulting image can be written to a memory stick using dd(1):

# dd if=i386memstick-5.0.1.img of=/dev/sd0d

Please note that this script depends on the sysutils/cdrtools package
for extracting the contents of the release ISO.

Hopefully this will be integrated with the build process so these
images are available for those who cannot prepare an image due to lack
of access to a NetBSD machine.
