Improve support of Enums

[Girgias]

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

• Better rendering
• Linking support in <type> and <enumname>
• Support for search
• Linking support for cases in <enumidentifier> and possibly <constant>

[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