datMap does not now try to always mmap even anonymously

Some calls to datMap involve very small data arrays so rather
than always using mmap() even when we can't mmap() a file the
code now calls cnfCalloc directly if the file can not be
mmapped.
No longer use the HDF5 HL interface

H5LT calls removed in commit 95467e090b85f190c559f4dd66381f80ce781b86
and this commit removes the library from the link command and the
include file from the source code.