[Bug target/53888] New: gthr-win32.h defines __gthread_mutex_destroy with wrong return type

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53888

             Bug #: 53888
           Summary: gthr-win32.h defines __gthread_mutex_destroy with
                    wrong return type
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: redi@gcc.gnu.org
            Target: *-mingw32


gthr.h documents the required function

     int __gthread_mutex_destroy (__gthread_mutex_t *mutex);

but gthr-win32.h defines:

static inline void
__gthread_mutex_destroy (__gthread_mutex_t *__mutex)
{
  __gthr_win32_mutex_destroy (__mutex);
}

This means code using __gthread_mutex_destroy can't check the return value, as
it would fail to compile on Windows.