[m-rev.] for review: Account for Winpthreads in configure.

[Julien Fischer]

On Wed, 13 Aug 2014, Peter Wang wrote:

> Branches: master, 14.01
>
> configure.ac:
> 	Always build Boehm GC with GC_WIN32_PTHREADS when pthread.h is
> 	detected on MinGW* systems.

Even in non par grades when parallel marking is not enabled?  What
pthreads calls could we make then then?   I think libc on MinGW-w64
requires winpthread to support some C11 features, so maybe it's always
needed on that system, but shouldn't it remain possible to build non
.par grades on plain MinGW without requiring pthreads?

>       Otherwise we risk making pthread calls which are not intercepted
>       by Boehm GC.

Cheers,
Julien.