Add an add_hosts_file routine that adds a "hosts" path to an array and

Add an add_hosts_file routine that adds a "hosts" path to an array and
use it in tshark.c instead of read_hosts_file. This lets us use "-H"
multiple times. Make read_hosts_file static.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@46273 f5534014-38df-0310-8fa8-9805f1628bb7