[573202] Added dedicated drag source feedback figure

In order to avoid strange drawing artifacts on Windows and MacOS we
provide our own drag source feedback figure.

This also harmonize the look and feel with the selection feedback
introduced in 4diac IDE 1.13.0

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=573202
Change-Id: I0a60d1c98cf92723e9f8de1158c90c8772148fb9
2 files changed