Transition from GeoIP Legacy to MaxMindDB.

Transition from GeoIP Legacy to MaxMindDB.

MaxMind is discontinuing its legacy databases in April in favor of
GeoIP2, which use a newer database format (MaxMind DB). The reference C
library (libmaxminddb) is available under the Apache 2.0 license which
isn't quite compatible with ours.

Add mmdbresolve, a utility that reads IPv4 and IPv6 addresses on stdin
and prints resolved information on stdout. Place it under a liberal
license (MIT) so that we can keep libmaxminddb at arm's length. Add
epan/maxmind_db.[ch], which spawns mmdbresolve and communicates with it
via stdio.

Migrate the preferences and documentation to MaxMindDB.

Change the IPv4 and IPv6 asnum fields to FT_UINT32s. Change the
geographic coordinate fields to FT_DOUBLEs.

Bug: 10658
Change-Id: I24aeed637bea1b41d173270bda413af230f4425f
Reviewed-on: https://code.wireshark.org/review/26214
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Gerald Combs <gerald@wireshark.org>