Qt documentation pages should mark snippets, class names ... as not translatable.

Motivation

Automated translation of webpages is becoming more and more popular. One can for instance translate a web page via Google Translate. Chrome supports this automatically by a 'translate' button.

Anyhow, when doing this for doc.qt.io, a couple of issues emerge:

• Code snippets like the qmake, CMake include lines for class information is partially translated too. For instance 'REQUIRED COMPONENTS' keywords in CMake become 'ERFODERLICHE COMPONENTEN'.
• Function names, types, and argument names are partially translated, too.
• Fixed names like 'Qt Core' or 'Qt Test' are translated, too

Proposed fixes

Code snippets, keywords ... should be marked with class="notranslate" in the generated html. This should be fairly easy to do as part of qdoc for fixed places. Anyhow, for module names etc we might have to enforce dedicated macros ...