[Darwine] Remove multi implementation of NtCurrentTeb

[maillard.emmanuel at libertysurf.fr]

Sorry the problem with NtAllocateVirtualMemory is in 
RtlCreateUserThread.

emmanuel

> NB : creating thread with wine-pthread still not work, because calling 
> NtAllocateVirtualMemory in start_thread always return 
> STATUS_INVALID_PARAMETER.