This largely copies over Spicy's `.clang-format` configuration file. The
one place where we deviate is header include order since Zeek depends on
headers being included in a certain order.
This opens up the possibility of storing other request types outside
of T_A, T_PTR and T_TXT without requiring redoing the caching. It
also fixes the caching code in DNS_Mapping, adding a version number
to the start of the cache file so the cache structure can be modified
and old caches invalidated more easily.
