Undo the escaped dot (\\.) decoding in decode()

On our platform at least (avahi-browse, Linux) this results in DNAMEs
containing periods having more DNS labels, which is wrong and breaks
things in DNS-SD resolving; mDNSResponder for example complains:

FoundInstance: _ipp._tcp.dns-sd.admin.grnet.gr. PTR
printer-color.admin.grnet.gr._ipp._tcp.dns-sd.admin.grnet.gr.
received from network is not valid DNS-SD service pointer

Relevant thread:
http://lists.apple.com/archives/bonjour-dev/2011/Jun/msg00026.html