Fixed all instances of warnings OpenJDK finds with -Xlint:unchecked.
Merging this will at least result in a dependency on JDK 1.5 or later
that I'm pretty sure of. But since the only JDKs that are really safe
to use these days are versions 1.8 and 9, that's probably okay.
No promises that this will make modern SWT work or anything, but it's
probably at least a beginnig toward that as well.
292afd24c9