vchoi_fork

[svn-r12374] Purpose:

1) Check in potential fix to unreproduceable bug in t_cache observed on
   Cobalt

2) Check in code supporting added pinned entry features in the metadata
   cache.


Description:

1) Elena encountered a bug in t_cache when running on Cobalt.  On
   investigation I found a potential race condition in t_cache that
   could explain her observation.

2) Quincey requested additions to the metadata cache allowing renaming
   of pinned entryies, and marking of pinned or protected entries as
   dirty.


Solution:

1) Modified t_cache.c to prevent the potential race condition.  Elena
   was unable to reproduce the bug on Cobalt, so we don't know if my
   fix actually addressed the problem.

2) Added code supporting the requested functions.  The changes were
   relatively trivial, but required substantial new test code.


Platforms tested:

h5committest, serial test on heping, parallel test on phoenix.


Misc. update: