Pull up following revision(s) (requested by uwe in ticket #884):

sys/arch/powerpc/powerpc/trap.c: revision 1.154

In mtmsr emulation ignore PSL_VEC we set in mfmsr emulation just
above, as it freaks out PSL_USEROK_P().  This is also congruent with
how we handle PSL_FP.

PR port-macppc/53360

(martin)