1.0.41.23: ppc: Calling-convention fixes for LRA handling during return.

1.0.41.23: ppc: Calling-convention fixes for LRA handling during return.

  * For GC purposes, seven times never clobber reg_CODE while still
within a component.

  * During return processing, store the LRA in reg_LRA instead of
reg_CODE (see previous point).

  * During fun end breakpoint processing, use reg_LRA instead of
reg_CODE to store the LRA object on ppc.

  * The upshot of this is that, during returns, the program counter
and link register can always be found within the body of reg_CODE
or reg_LRA, no matter which side of the blr instruction we check,
thus always allowing the GC to correctly update them.