Scheduler: free a task's ELF image.

Now that we have support for larger pages, this works!!

kernel/src/thread/Scheduler.cpp

@@ -162,6 +162,7 @@ void Scheduler::reap_task(Task* task)
         {
             ELFSection& section = exiting_task->image->sections[i];
             kdbgln("Task was using region %lx, which used %ld pages", section.base, section.pages);
+            MemoryManager::release_pages((void*)section.base, section.pages);
         }
         kfree(exiting_task->image);
     }