hdf5_chunking_query_bmr

[svn-r16199] Added HDlseek in front of the truncate function in H5FD_sec2_truncate for VMS only.  
On Open VMS, if the last read or write put the file pointer beyond the current file size 
(it happens when an object is deleted), the file can be extended when it's truncated.

Tested on VMS.