Huge memory usage when VLC is fresh started

I currently get a 1040 MB memory usage when loading a 4.0 nightly, even with --no-media-library.

It appears this change occured between the 2018-06-16 and 2018-06-19, when the old UI was still used. The memory went from 150 MB to 550 MB. During that time we switched to from Qt 5.6 to Qt 5.11. Using the libqt_plugin.dll from the 16th in the 19th build fixes the memory issue, using the libqt_plugin.dll from the 19th in the 16th build exhibits the issue.

I don't know if the same issue exists on Linux.

The nightly builds and my local build are using debug builds. I don't know if the same issue exists in release builds. We always build Qt with -release so it's unlikely to make a difference.