* sim-bits.h (_MSB_16, _LSB_16): Define for 16-bit targets.
(MASK, LSBIT, MSBIT): Likewise and use _MSB_16 and _LSB_16.
(EXTENDED): Define for 16-bit word size.
* sim-bits.c (LSEXTRACTED, MSEXTRACTED, LSINSERTED,
MSINSERTED, LSSEXT, MSSEXT): Implement for 16-bit word size.
* sim-types.h: Added support for 16-bit targets.