New pthreads library

[Roland McGrath]

> Roland McGrath <frob@MIT.EDU> writes:
> 
> > Ah, yes.  That is what you will get for:
> > 
> > 	extern struct foo seg asm("%gs:0");
> > 	... = &seg;
> 
> We'll see whether we can work around this.  Maybe it's never necessary.

That's what I was thinking.  If only macros that use this is are "access
member of current thread's descriptor", then it should never come up at all.
But you probably do need to completely avoid assigning any variables to
`&seg', because without optimization the compiler will emit the bogus
instructions attempting to take the address of the segment register.