Quirks.cpp: Fix and extend domain method

[Karl Dubost]

bool Quirks::isDomain(const String& domainString) const
{
    return RegistrableDomain(m_document->topDocument().url()).string() == domainString;
}

was added with 
Bug 260938
https://github.com/WebKit/WebKit/pull/17329

but it broke at least one Quirk Bug 267569

Indeed 
Quirks::isDomain("www.example.com") will return false
Quirks::isDomain("example.com") will return true

because RegistrableDomain(m_document->topDocument().url()).string()
returns only the top domain.

So probably we need something along

Quirks::isFullDomain("www.example.com") matches only www.example.com
Quirks::isTopDomain("example.com")      matches only example.com

And maybe something along 
Quirks::isSubDomain("example.com") matching everything *.example.com

Real names to be determined.

[Anne van Kesteren]

isDomain should be renamed to isRegistrableDomain or maybe even topLevelDocumentRegistrableDomainIs.

However it's not clear you want isRegistrableDomain to begin with here. After all, it can lead to bug 267569 happening. I would expect these to be useful:

- topLevelDocumentDomainIs
- topLevelDocumentDomainIsSubDomainOf / topLevelDocumentDomainEndsWith

[Radar WebKit Bug Importer]

<rdar://problem/121499128>