[PATCH roland/vdso_clock_gettime] x86: Clean up __vdso_clock_gettime variable.

[Roland McGrath]

> Since you are modifying the code, which are the advantages and constrains to
> x86_64/i386 carry specific assembly implementation for pthread_cond_* 
> function? What prevent them to use the C default code? 

We've discussed before that we'd like to eliminate the assembly.  We have
just been too conservative to do it without careful performance testing to
give us confidence that it won't be a performance regression, and nobody
has done that yet.  I think it might be on Torvald's agenda.  (If not, we
need a volunteer for that!)