vchoi_fork

[svn-r12348] Purpose:
Bug fix.

Description:
Some machines (e.g., HPUX) will have off64_t defined but no support
for stat64 unless certain LargeFile macro is turned on.  This caused
the last fix on H5private not quite right which caused compiling failures.

Solution:
Added stat64 and fstat64 tests and then will use them only if they
are supported.

Platforms tested:
Tested on kelgia, copper and heping (pll).
(Compiling alright but tests for kelgia and heping are not done.
expect no problems.)