Add microseconds to error log

[mikhainin]

It's just a first attempt to complete #9745

[TysonAndre]

This appears to implement the functionality being discussed on the mailing list correctly, e.g. u is always 6 digits long, and the args change and the parts of the code being changed seems right.

This PR is properly using u - https://www.php.net/manual/en/datetime.format.php#refsect1-datetime.format-parameters

			case 'u': length = slprintf(buffer, sizeof(buffer), "%06d", (int) floor(t->us)); break;

[mikhainin]

Not sure if I'm happy with such a solution (option error_log_usec doesn't look quite elegant, maybe rename it?)
But now we have backward compatibility.

$ ./sapi/cli/php -derror_log=/dev/stdout -r 'error_log("test");'
[11-Nov-2022 13:45:33 UTC] test

$ ./sapi/cli/php -derror_log=/dev/stdout -derror_log_usec=on -r 'error_log("test");'
[11-Nov-2022 13:45:45.926149 UTC] test

Shall I mention this change in the thread? It looked like people were a bit annoyed by me last time...

[bukka]

Looks reasonable to me. Just some minor things to change.

About the name it's probably best to mentioned in the internals thread. Personally I don't mind this name but maybe someone else might suggest something better.

[bukka]

It should be in the usec condition where this actually matters

[mikhainin]

done, thanks. If you take a look once again, please?

[derickr]

As I have just explained on the mailinglist, I don't think we should merge this at all. Your operating system already provides all the functionality to show these microseconds: https://news-web.php.net/php.internals/119046

[bukka]

@negram I think that the discussion on internals didn't reach an agreement so this might need an RFC. Are you prepared to do that? If not, we should close this PR.

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