pthread_barrier type and functions

[Mohammad Akhlaghi]

Dear Gnulib team,

This is Mohammad Akhlaghi, I am the maintainer of the GNU Astronomy 
Utilities (gnuastro). Gnuastro was dubbed as a GNU package a few weeks 
ago will soon be publicly released (as soon as the copyrights are all 
given to the FSF).

I have just started using Gnulib to make gnuastro available to users of 
other operating systems. It is truely fantastic, thank you so much for 
all the efforts for this wonderful library. I have made lots of use of 
the GNU C library functions (like argp and error) and Gnulib worked 
great. But I have a problem with pthread_barrier_* types and functions.

I have made extensive use of the pthread_barrier_* types and functions 
for the parallel processing parts of gnuastro. But I found out Gnulib 
doesn't include them. I wanted to see if it would be possible for you to 
include these in the Gnulib version of pthread. Using a pthread_barrier 
is simpler than using a mutex and condition variable together when the 
jobs are completely independent.

Thank you very much,
Mohammad