runtime/thread.h: Fix non-thread binding and control stack pointer access.

runtime/thread.h: Fix non-thread binding and control stack pointer access.

  * In the non-threaded case, these macros used to break up into two
groups, one for x86oids and one for everything else.  This is wrong
just as soon as a non-x86oid port uses a static symbol for the binding
stack pointer.

  * Reorganize the non-threaded cases to parallel the structure of the
threaded case, dispatching on the presense of the static symbol for
binding stack access and specifically detecting non-x86oids for the
control frame pointer access.