files: pf.os: merge the signatures splitted by version

files: pf.os: merge the signatures splitted by version

In order to be able to identify the OS version we need to merge the signatures
split by version. eg.

65535:64:1:60:M*,N,W1,N,N,T:	FreeBSD:4.7-4.11::FreeBSD 4.7-5.2
65535:64:1:60:M*,N,W1,N,N,T:	FreeBSD:5.0-5.2::FreeBSD 4.7-5.2

65535:64:1:60:M*,N,W1,N,N,T:	FreeBSD:4.7-5.2::FreeBSD 4.7-5.2

Fingerprints need to be unique to make this fit into the set/map
infrastructure for exact matches. Having multiples fingerprints with
same signature is a problem, since it forces users to add multiple
rules.

Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>