For the record (since I think we only talked about this on IRC):
* the POSIX TLS fallback code doesn't work on Linux hosts for
linux-user emulation (the constructor is never called to set up
the TLS for the main thread, probably something to do with our
custom linker script, since it does work OK for system emulation)
* if I recall correctly from IRC it doesn't compile on OpenBSD
so for 1.0 perhaps we need to fall back to a simpler set of patches
that just avoid the regression in thread support for linux-user ?