GCC generates better code when multiplication operations, which require
library functions to perform, are caught in early in RTL, rather than
leaving the operation to be mapped to a library function later on.

When there is hardware multiply support, it is more efficient to perform
widening multiplication using the hardware multiplier instead of letting
GCC widen the arguments before calling the multiplication routine in the
wider mode.

Successfully regtested GCC and G++ testsuites for:
    msp430-sim
    msp430-sim/-mcpu=msp430
    msp430-sim/-mhwmult=f5series
    msp430-sim/-mhwmult=f5series/-mlarge/-mdata-region=either/-mcode-region=either
    msp430-sim/-mlarge
    msp430-sim/-mlarge/-mdata-region=either/-mcode-region=either

Additionally regtested GCC execute.exp for:
    msp430-sim/-mhwmult=16bit
    msp430-sim/-mhwmult=32bit
    msp430-sim/-mhwmult=f5series
    msp430-sim/-mhwmult=none
    msp430-sim/-mlarge/-mcode-region=either/-mdata-region=either/-mhwmult=16bit
    msp430-sim/-mlarge/-mcode-region=either/-mdata-region=either/-mhwmult=32bit
    msp430-sim/-mlarge/-mcode-region=either/-mdata-region=either/-mhwmult=f5series
    msp430-sim/-mlarge/-mcode-region=either/-mdata-region=either/-mhwmult=none

Ok for trunk?