The mls instruction computes accumulator - product, but the simulator
accidentally has the subtract operands swapped.  While writing the
testcase for this problem, I discovered that the movi instruction is
broken, there is a missing break after the half word support.  Both
are simple fixes.

The testcase works with the patch, and fails without the patch.  The
mls fix takes GCC C testsuite failures from 2407 to 2406, and the movi
fix then takes it from 2406 to 2295.

Jim