libxt_hashlimit: add support for byte-based operation

libxt_hashlimit: add support for byte-based operation

allows --hashlimit-(upto|above) Xb/s [ --hashlimit-burst Yb ]
to make hashlimit match when X bytes/second are exceeded;
optionally, Y bytes will not be matched (i.e. bursted).

[ Pablo fixed minor compilation warning in this patch with gcc-4.6 and x86_64 ]

libxt_hashlimit.c: In function ‘parse_bytes’:
libxt_hashlimit.c:216:6: warning: format ‘%llu’ expects argument of type ‘long long unsigned int’, but argument 3 has type ‘uint64_t’ [-Wformat]

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>