Allow traceroute -w values down to 1 second, from John Carmack

Allow traceroute -w values down to 1 second, from John Carmack
Change the default -w from 5 to 3 seconds, reducing the time it waits
for a response. John proposed using 1 second for this, but several
of us are familiar with networks where that would be likely to
remove hops, 3 seems reasonable and still saves 6 seconds on a
non-responding hop (there's always mtr if you need faster output).
Feedback from various, ok phessler@ kn@ florian@