Ability to run on JDK 11
Ability to run on JDK 11

JDK 11 seems to have outright removed this SoftCache class which was being
used by GhostToolkit. Apparently this class was just a simple map which Java
itself replaced with a HashMap<K, SoftReference<V>> wherever it was used,
so I made the same changes here.

Danielku15/GhostAWT,Danielku15/GhostAWT