vchoi_fork

[svn-r12751] Purpose:
Bug fix (related to 544)

Description:
h5_get_file_size() was coded to return 0 if failed but
file size can be 0.  Changed the failure return value to -1
which is allowed by the returned type of off_t which is a signed
type.
Also changed the checking code of the stat call to just == 0
since that is how it is defined.

Test:
Could test it in heping only.  Both Sol and Copper failed to
compiled due to error in the Direct IO VFD code.