1.0.41.28: ppc: Fix race conditions in use of pseudo-atomic in ppc-assem.S.

1.0.41.28: ppc: Fix race conditions in use of pseudo-atomic in ppc-assem.S.

  * Originally, ppc-assem.S was saving the pseudo-atomic-interrupted
bit before clearing the pseduo-atomc-atomic bit in reg_ALLOC.  This
introduces a single-instruction window wherein an interrupt could
occur, be deferred, and the setting of pseudo-atomic-interrupted be
ignored.

  * Fixed, in the four places it occurs, by reordering instructions.