hdf5_ep

[svn-r15630] Description:

In nh5tget_offset_c:

(1) The return value type of H5Tget_offset was set to size_t where
    it should be of type int.

(2) Was if offset was equal to 0 it returned the error code of -1 back to 
    Fortran, this was changed to return an error code of -1 when the
    offset value is < 0.

In h5tget_norm_c:

(1) was if the return value of H5Tget_norm = 0 it would return an error
code to Fortran, but from enum of the return value:

typedef enum H5T_norm_t {
    H5T_NORM_ERROR       = -1,  /*error                                      */
    H5T_NORM_IMPLIED     = 0,   /*msb of mantissa isn't stored, always 1     */
    H5T_NORM_MSBSET      = 1,   /*msb of mantissa is always 1                */
    H5T_NORM_NONE        = 2    /*not normalized                             */
    /*H5T_NORM_NONE must be last */
} H5T_norm_t;

only when -1 is returned is there an error, changed it to return an error 
only if the value of H5T_NORM_ERROR = -1.