1.0.41.34: ppc: Implement multithreaded symbol binding / unbinding.

1.0.41.34: ppc: Implement multithreaded symbol binding / unbinding.

  * This is roughly based on the x86-64 version, but with TLS
allocation inline and synchronization made up with a copy of
"The PowerPC Architecture" in front of me.

  * This does not have any check for TLS index overflow.

  * Also implement the spinlock stuff used by the runtime to
do its TLS index allocation for dynamic binding.