Allow db:modifier after db:methodname and the parameters in db:constructorsynopsis

[dourouc05]

This allows the description to match more language syntaxes, like C++. My use case is the following:

<db:constructorsynopsis>
<db:methodname>QXmlStreamWriter</db:methodname>
<db:methodparam>
<db:type>QString *</db:type>
<db:parameter>string</db:parameter>
</db:methodparam>
<db:modifier>overload</db:modifier>
<db:synopsisinfo role="meta">constructor</db:synopsisinfo>
<db:synopsisinfo role="overload-number">3</db:synopsisinfo>
<db:synopsisinfo role="signature">QXmlStreamWriter(QString *string)</db:synopsisinfo>
<db:synopsisinfo role="access">public</db:synopsisinfo>
<db:synopsisinfo role="status">active</db:synopsisinfo>
<db:synopsisinfo role="threadsafeness">unspecified</db:synopsisinfo>
</db:constructorsynopsis>

This is a description of https://doc.qt.io/qt-6/qxmlstreamwriter.html#QXmlStreamWriter-3

[ndw]

More generally, it looks like db:modifier should be allowed after classname in ooclass, interfacename in oointerface, exceptionname in ooexception, varname in fieldsynopsis, methodname in constructorsynopsis (as you suggest), methodname in destructorsynopsis, and enumname in enumsynopsis.

I see that it's already allowed after parameter in methodparam, templatename in template, package in packagesynopsis, macroname in macrosynopsis, macrodef in macroprototype, unionname in unionsynopsis,
and typedefname in typedefsynopsis.

[ndw]

Subsumed by #235.