Don't use a global capture_opts in the capturing engine (this isn't a good idea)...

Don't use a global capture_opts in the capturing engine (this isn't a good idea). Do some more "housekeeping" in the capturing part.

Hopefully the unspecified forward declaration of capture_options_t in main.h is portable, but buildbot will tell me. This way I need the internals of that struct only at the places I really use it.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@12853 f5534014-38df-0310-8fa8-9805f1628bb7