MySQLi: Fix incorrect XML IDs for constant linking

[Girgias]

Found via a new documentation tool I am working on.

[haszi]

I'm wondering whether we should include something in either doc-base/configure.php or PhD that would check existing IDs against the contents of <function>, <methodname>, <constant>, etc. tags which could give us an idea of the extent of similar issues.

[Girgias]

I'm wondering whether we should include something in either doc-base/configure.php or PhD that would check existing IDs against the contents of <function>, <methodname>, <constant>, etc. tags which could give us an idea of the extent of similar issues.

Maybe, but it might be a bit tricky? I have added this to check in https://github.com/Girgias/stub-to-docbook, and it should be possible to use it to write some sort of report about the current status of constants. But a lot of them don't even seem to have IDs in external extensions.