1.0.41.32: ppc: Random small threading bits.

1.0.41.32: ppc: Random small threading bits.

  * Thread-specific static symbols (these should probably be
moved to the list of common static symbols).

  * The reader for random TLS data, current-thread-offset-sap.

  * On threaded targets, stepping is controlled by a slot in the
thread structure, not by a static-symbol.  Fixed.

  * On non-threaded targets, don't hit the static-symbol value with
yet another ad-hoc method of calculating the address, use the
existing load-symbol-value macro.