hdf5_der

Checkin of merge of cache image feature into page buffering and
integration of cache image into file shutdown mods as adapted to
paged allocation.

This checkin has a number of issues:

1) test_filespace_round_compatible() in tfile.c fails.  This failure
   appears to be the result of the file format change for the free space
   manager SBE message.  The issues appears to have been exposed by
   the addition of cache image and its SBE message.

   The test is commented out pending resolution of this issue.

2) 6 assertion failures in the tests for h5stat.  While I haven't investigated
   these carefully, my guess is that they are also due to the file format
   change.

3) There is an issue with testh5mkgrp.sh.  At first glance it appears
   to be caused by the loss of the tools/test/misc/testfiles directory
   and its contents most likely on execution of make distclean.

4) At present, if either H5MF_alloc(), H5MF_xfree(), H5MF_try_close(),
   or H5MF_get_free_sections() are called before the first metadata cache
   access when opening a file with an existing cache image, we should
   trigger an assertion failure.

   This condition should be impossible in the calls to H5MF_alloc(), and
   H5MF_xfree().  However it is possible in H5MF_get_free_sections() and
   it may be possible in H5MF_try_close().

   The solution is easy enough for H5MF_get_free_sections(), but I need to
   write the appropriate test code.  As for H5MF_try_close(), I need to either
   verify that the condition cannot hold, or apply the same fix as per
   H5MF_get_free_sections().

5) Constructing cache image and page buffering should be disabled in the
   parallel case.  Must verify this.

6) Loading a file with an existing cache image should work in the parallel
   case.  Must write test code to verify this.

7) Must verify that either the persistant free space managers are disabled
   in the parallel case, or that they work correctly.  In the latter case,
   must verify that an existing cache image plays nicely with them.

Test serial, serial/production, and parallel on Jelly and Mercury.