parser: allow ct timeouts to use time_spec values

parser: allow ct timeouts to use time_spec values

For some reason the parser only allows raw numbers (seconds)
for ct timeouts, e.g.

ct timeout ttcp {
	protocol tcp;
	policy = { syn_sent : 3, ...

Also permit time_spec, e.g. "established : 5d".
Print the nicer time formats on output, but retain
raw numbers support on input for compatibility.

Signed-off-by: Florian Westphal <fw@strlen.de>