Unify parse_argv style

getopt is usually good at printing out a nice error message when
commandline options are invalid. It distinguishes between an unknown
option and a known option with a missing arg. It is better to let it
do its job and not use opterr=0 unless we actually want to suppress
messages. So remove opterr=0 in the few places where it wasn't really
useful.

When an error in options is encountered, we should not print a lengthy
help() and overwhelm the user, when we know precisely what is wrong
with the commandline. In addition, since help() prints to stdout, it
should not be used except when requested with -h or --help.

Also, simplify things here and there.
tty-ask-password-agent: modernization
resolved: align last rr column
build-sys: use a common rule for some gperf commands
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.
resolve-host: make arg_type an int

We are using it also to store _DNS_TYPE_INVALID, so it should be signed.
resolved: DNSKEY records
resolved: add identifiers for dnssec algorithms
resolved: RRSIG records