Fix failing Travis CI build (e.g.:

Fix failing Travis CI build (e.g.:
https://travis-ci.org/#!/mcr/tcpdump/builds/2786065)

Remove hacky patching of `configure.in` because this is now redundant
with the change that was accepted in
https://github.com/mcr/tcpdump/pull/32 and it causes patch to prompt for
whether to reverse the patch which makes the Travis build time out.