Public survey: PThread support on target systems

[Jan Maria Matejka]

Hello all!

> Please answer a simple question:
> **Do you run BIRD on anything that has no or broken pthread support?**

After several responses, I'm adding, HOW to check this.

If you run BFD in BIRD, you HAVE pthread support.
If you don't have <pthread.h> #include, you don't have pthread support.

If you run BIRD on common recent Linux or BSD (let's say not older than 5 years)
on some common architecture (i386, amd64, arm*), it's also pretty sure that
you have pthread support.

If your compiler doesn't know anything about threads, you also don't
have pthread support (grep the manpage, e.g. `man gcc | grep pthread`)

If you run BIRD on Android, you probably support pthreads but spinlocks
(needed by BFD) have been added to libbionic quite recently so you can't
run BFD but you still support enough pthreads.

If you still don't know, please specify what do you have and we'll try to help you.

Maria