IN: Sign position, i.e., the bit offset of the floating-point sign bit
IN: Exponent bit position
IN: Size of exponent in bits
IN: Mantissa bit position
IN: Size of mantissa in bits
H5T_SET_FIELDS sets the locations and sizes of the various floating-point bit fields. The field positions are bit positions in the significant region of the datatype. Bits are numbered with the least significant bit number zero.
Fields are not allowed to extend beyond the number of bits of precision, nor are they allowed to overlap with one another.
Returns a non-negative value if successful; otherwise returns a negative value.