Fix an incorrect use of the operand union in the vm
Fix an incorrect use of the operand union in the vm

The mul instruction was access registers using .integer and not
.reg.  Most compilers allow this but it's not valid C.

Signed-off-by: Mark Ryan <88ffc4093c40652fbbf052f026a8b6147509f0aa@gmail.com>

markdryan/subtilis,markdryan/subtilis