Set dest to non-zero if the core supports the MT ASE, else zero. If MT is not supported then branch to nomt.

This is similar to load_up_altivec but for the transactional version of the vector regs. It doesn t mess with the task MSR or valid flags. Furthermore, VEC laziness is not supported with TM currently.

Used for splitting without copying. No attempt is made to handle too large indexed vertex buffers: In general you need to copy to do that.