Improve support of Enums

[Girgias]

Following the most basic of supports in #179 I think it is necessary to improve it:

• Better rendering (Partial fix Render enumitemdescription using single line comments #192)
• Linking support in <type> and <enumname>
• Support for search (Add "enum." to manual search sections web-php#1238)
• Linking support for cases in <enumidentifier> and possibly <constant>
• Add support enum links #188
• Support enum display version info #191
• Support namespace declares (see [Bug] The documentation of the Pcntl\QosClass enum shows a broken synopsis doc-en#4516)

[TimWolla]

Better rendering

To explicitly spell that out: Currently the doc comments are confusingly placed below the respective case, which can lead to off-by-one errors for users reading the docs.

[haszi]

• Linking support in <type> and <enumname>

<type> would be used in parameters or return types and <enumname> more or less everywhere elsewhere, right?

• Linking support for cases in <enumidentifier> and possibly <constant>

<enumidentifier> could probably be added relatively easily as long as we define xml IDs on the enum definition pages and use FQNs elsewhere. If nobody beats me to it, I'll take a look at this.

• Support for search

I think searching for the enum names is already working. Or do you mean searching for the cases/<enumidentifier>s?

[Girgias]

• Linking support in <type> and <enumname>

<type> would be used in parameters or return types and <enumname> more or less everywhere elsewhere, right?

What I meant is that <type> tags should be able to understand enumerations and be able to link to the correct page :)
See: https://www.php.net/manual/en/function.bcround.php for what I mean.

• Linking support for cases in <enumidentifier> and possibly <constant>

<enumidentifier> could probably be added relatively easily as long as we define xml IDs on the enum definition pages and use FQNs elsewhere. If nobody beats me to it, I'll take a look at this.

• Support for search

I think searching for the enum names is already working. Or do you mean searching for the cases/<enumidentifier>s?

Oh I didn't check, but being able to search for cases would be nice yes.

[TimWolla]

php/doc-en#4371 also appears to be a PHD issue, as the versions are in versions.xml:

https://github.com/php/doc-en/blob/4d8af0862acd95744e96db9e611a9e6c1b02521e/reference/random/versions.xml#L100

[alfsb]

I was wondering if is possible to embed these version details as <!--version from="" --> comments, inside each functionsynopisys/methodsynopsys, so detecting/debugging would be also simpler.

One thing I plan to work on this year is to move all PhD stuff inside configure.php to after manual.xml loading and validation is done, so the time to error is not impacted by processing PhD stuff, that is discarted anyways, if there is a loading or validation fail of manual.xml.