contiki-os/contiki — pull request #82 by darconeous (2013-01-11 17:54:11+00:00)
Title: Makefiles: Allow setting UIP_CONF_IPV6=0 to work as expected. 

Setting UIP_CONF_IPV6 to zero from the make build command line is
something that seems like it should ensure that IPv6 is disabled, but in
fact it actually *enables* IPv6. This seems counter intuitive, so this
patch changes the behavior of the makefiles to handle this case
properly.