Coverity complains about a missing fclose() in a non-existing
destructor. Also sprinkle in a strerror() call for fopen() to
provide a bit of a hint what might have gone wrong.
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.
- reporting of potentially sensitive constants
- tracking of unsupported types enabling hand-editing to fix them
- fixed generation of "unspecified" aggregates
- fixed generation of IPv6 constants
- fixed generation when running without a packet source
