resolve: add more record types and convert to gperf table

resolve: add more record types and convert to gperf table

We are unlikely to evert support most of them, but we can at least
display the types properly.

The list is taken from the IANA list.

The table of number->name mappings is converted to a switch
statement. gcc does a nice job of optimizing lookup (when optimization
is enabled).

systemd-resolve-host -t is now case insensitive.