Revert "Merge pull request #591 from pinwing/ipv6"

This reverts commit 929812dad7ad78c355b7a598feb0a4ae100b2b20, reversing
changes made to 264a673aef9b5ffec41362fe37c0a37d0709de9f.

Conflicts:
	release/src/router/rc/services.c
	release/src/router/rc/udhcpc.c
	release/src/router/shared/defaults.c
Merge pull request #651 from pinwing/ipv6

Revert "Merge pull request #591 from pinwing/ipv6"