hdf5

[svn-r17532] Purpose: Fix bug 1555

Description:
At several places in H5Pint.c properties were being compared using memcmp, not
using the registered "cmp" callback.  This could cause memory checkers to
report uninitialized memory errors, and could conceivably cause runtime errors
if memcmp reported false equality (for example if a value pointed to by the
property changed).

The code has been changed to always use the cmp callback.  No tests have been
added as the cmp callback is not exposed in the 1.6 API.

Tested: jam, linew, smirom (h5committest)