Handle subclasses of Exception in drb

This makes it so that client instances that call a method on a
server-side object that raise a subclass of Exception are handled
similarly to those that raise a subclass of StandardError.

Only reraise exceptions that we are fairly sure we don't want to
rescue.

Fixes [Bug #5618]

lib/drb/drb.rb

@@ -1701,7 +1701,9 @@ module DRb
           end
         end
         return @succ, @result
-      rescue StandardError, ScriptError, Interrupt
+      rescue NoMemoryError, SystemExit, SystemStackError, SecurityError
+        raise
+      rescue Exception
         @result = $!
         return @succ, @result
       end