Show both build and runtime versions of Qt

[softins]

Short description of changes

Displays both the version of Qt the executable was built with, and the version currently running via the dynamic libraries. These are available from QT_VERSION_STR and qVersion() respectively.

jamulus --version now shows something like:

 *** This app uses the following libraries, resources or code snippets:
 *** 
 *** Qt cross-platform application framework 5.9.5 (build), 5.15.2 (runtime)
 *** <https://www.qt.io>

About Jamulus.. / Libraries shows the same information.

CHANGELOG: Client/Server: Display Qt versions for both build and runtime.

Context: Fixes an issue?

Fixes: #3230

Does this change need documentation? What needs to be documented and how?

No

Status of this Pull Request

Tested and ready to merge.

What is missing until this pull request can be merged?

Just review

Checklist

• I've verified that this Pull Request follows the general code principles
• I tested my code and it does what I want
• My code follows the style guide
• I waited some time after this Pull Request was opened and all GitHub checks completed without errors.
• I've filled all the content above

[ann0see]

Seems ok now to me.