[ 1967938 ] Find All Highlights Never Removed
https://sourceforge.net/tracker/?func=detail&atid=438935&aid=1967938&group_id=44253
In revision 4482, a loop calling removeRegion for every
region removed by clearRegions() and removeRegions(OpenDefinitionsDocument)
was removed and replaced by a simple call to clear() of the underlying
data structure. This did not notify the listeners anymore that regions
were removed, causing the highlights never to be removed.
M src/edu/rice/cs/drjava/model/ConcreteRegionManager.java
