darwin: fix compilation errors with -DMURPHI=OFF -DGUI=OFF -DRX_PATH=
* hoard/heaplayers/threadheap.h, hoard/userealtls.cpp, tools/probabilistic.cpp, wibble/empty.h, wibble/mixin.h, wibble/range.h, wibble/singleton.h: here.
* hoard/heaplayers/threadheap.h, hoard/userealtls.cpp, tools/probabilistic.cpp, wibble/empty.h, wibble/mixin.h, wibble/range.h, wibble/singleton.h: here.