sun.misc.Cleaner used in MemMappedCharSequence

[Former user]

Original [issue 69](https://code.google.com/p/okapi/issues/detail?id=69) created by @ysavourel on 2009-05-11T23:06:34.000Z:

Need to replace or integrate because it may not implemented for different VMs.

[Former user]

Comment [1.](https://code.google.com/p/okapi/issues/detail?id=69#c1) originally posted by @ysavourel on 2009-05-22T20:39:41.000Z:

I commented out this code for now.

[Former user]

Comment [2.](https://code.google.com/p/okapi/issues/detail?id=69#c2) originally posted by @ysavourel on 2011-08-04T13:22:07.000Z:

AccessController.doPrivileged() no longer used.