fix a rookie mistake causing Singleton<> to be a "multiton". Also improve the...

fix a rookie mistake causing Singleton<> to be a "multiton". Also improve the BufferMapper's debugging, but turn it off.

Squashed commit of the following:

commit 04e9cae7f806bd65f2cfe35c011b47a36773bbe5
Author: Mathias Agopian <mathias@google.com>
Date:   Wed Apr 15 18:30:30 2009 -0700

    fix and improve BufferMapper's tracking of mapped buffers.

commit 1a8deaed15811092b2349cc3c40cafb5f722046c
Author: Mathias Agopian <mathias@google.com>
Date:   Wed Apr 15 00:52:02 2009 -0700

    fix some bugs with the Singleton<> class. untested.

commit ed01cc06ad70cf640ce1258f01189cb1a96fd3a8
Author: Mathias Agopian <mathias@google.com>
Date:   Tue Apr 14 19:29:25 2009 -0700

    some work to debug the Singleton<> template.