(thrown in TimSort.mergeHi)

Don't use DecoratingStyledCellLabelProvider or DecoratingLabelProvider
for sorting, see bug 364735 comment 60 and bug 512637 comment 1. The
results from such label providers are unstable by design and may
change during the sort operation. Instead, use the original label
provider enclosed by them.

Use system property introduced in bug 364735 to restore the old behavior
in case someone relies on the decorations for sorting:
"eclipse.disable.fix.for.bug364735". If this system property is set to
"true", this fix will be disabled.

Change-Id: I979649b163950f862733403184ef407afc82c767
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>