-/* Unpack a bitfield of the specified FIELD_TYPE, from the object at
- VALADDR, and store the result in *RESULT.
- The bitfield starts at BITPOS bits and contains BITSIZE bits; if
- BITSIZE is zero, then the length is taken from FIELD_TYPE.
-
- Extracting bits depends on endianness of the machine. Compute the
- number of least significant bits to discard. For big endian machines,
- we compute the total number of bits in the anonymous object, subtract
- off the bit count from the MSB of the object to the MSB of the
- bitfield, then the size of the bitfield, which leaves the LSB discard
- count. For little endian machines, the discard count is simply the
- number of bits from the LSB of the anonymous object to the LSB of the
- bitfield.
-
- If the field is signed, we also do sign extension. */