As register names are required for darwin, but not accepted by gas
unless you use `-mregnames', they have been conditionally removed on
non-darwin targets.
To avoid duplicating large blocks of almost identical code, the inline
assembly is now statically generated.
libphobos/ChangeLog:
* libdruntime/core/thread/osthread.d (callWithStackShell): Statically
generate PPC and PPC64 asm implementations, and conditionally remove
PPC register names on non-Darwin targets.