Add debian squeeze image

For folks who need "oldstable" (may God have mercy on their souls).

library/debian

@@ -5,3 +5,6 @@ wheezy	git://github.com/tianon/docker-brew-debian	C:8cca9c1bba4aa246ca71b8967700
 jessie	git://github.com/tianon/docker-brew-debian	C:51bf81b164ec5e788099136cbe9dd9e141140d4c
 
 sid		git://github.com/tianon/docker-brew-debian	C:d532462cfbae0d9809c3c24f9855291bf1142c1a
+
+squeeze	git://github.com/tianon/docker-brew-debian	C:af59cb2f4237f07713a369ee7def53bad7e46506
+6.0.8	git://github.com/tianon/docker-brew-debian	C:af59cb2f4237f07713a369ee7def53bad7e46506