FontMetrics fix - add QT version check so 5.10 is still OK.

QFontMetrics::horizontalAdvance was introduced in 5.11.

@john.tourtellott

Warnings:

• please consider adding a changelog entry in a file ending with .md in doc/release/notes.

The warnings do not need to be fixed, but it is recommended to do so.

Do: test

This merge request has been queued for testing. Test results may be viewed on:

• Internal CDash (master)
• CDash (master)
• Buildbot (master) (only visible from inside Kitware)

Branch-at-master: ee39c2a1

+1 Thanks a bunch, Aron

Do: merge

merged

mentioned in commit cf6cf94a