According to
https://developer.apple.com/documentation/dnssd/1804733-dnsserviceregister
the DNSServiceRef is initialized only if DNSServiceRegister() returns
kDNSServiceErr_NoError.  The faulty error handling code could
therefore crash.

Preparing for a variant of TimerEvent with coarse 1-second
granularity, but cheaper (with a timer wheel).

zeroconf/ZeroconfBonjour: Fix compile errors resulting from "refactor to SocketEvent" and reenable bonjour for darwin build

Similar to commits 1686f4e8 and
30a5dd26

"DEFAULT" is a bad name - all it says is that it's the default value,
but it doesn't say what it means.  The name NOTICE mimics the syslog
level.

These flags are output-only.

[[maybe_unused]] (introduced in C++17) is standard C++.

https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
says that this is equivalent to the GNU unused attribute.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The former was deprecated with C++14. The standard says they are the same
with one exception:

The header<climits>defines all macros the same as the C standard library
header<limits.h>.

[Note:The types of the constants defined by macros in<climits>are not
required to match the types to which themacros refer.— end note]
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Found with modernize-use-override
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Prevents compiling those sources many times, once for each debug
program using it.

Keep the SocketMonitor registered.  This wrong return value was added
6 years ago in commit 72cf8dd8, andd
apparently, nobody ever noticed.

Since we switched from autotools to Meson in commit
94592c14, we don't need to include
`config.h` early to properly enable large file support.  Meson passes
the required macros on the compiler command line instead of defining
them in `config.h`.

This means we can include `config.h` at any time, whenever we want to
check its macros, and there are no ordering constraints.

`HOST_NAME_MAX` is not a portable macro; it is undefined on some
systems.

Closes #402

std::regex_replace() is heavily bloated and overkill for this feature.