vchoi_fork

[svn-r11415] Purpose: Internal design change.

Description: H5T_register() replaces any existing data conversion path
with a new path.

Solution: Added a parameter to H5T_register() and H5T_path_find() to
signal the library whether the new conversion path is from API function
H5Tregister() or from private function like H5T_init_interface().  If it
is from H5Tregister(), replace existing path.  If it's from H5T_init_interface()
and the library is trying to register default hard conversion functions,
don't replace existing path because the path is registered by the library.
For example, the library registered H5T_conv_int_float() and is trying to
register H5T_conv_long_float().  The size of long is equal to int.  There's
no need to replace the path H5T_conv_int_float().

Platforms tested: h5committest and fuss.