Enable thread support in the MS-Windows build.

 src/systhread.h (w32thread_critsect, w32thread_cond_t, sys_mutex_t)
 (sys_cond_t, sys_thread_t) [WINDOWSNT]: New data types.
 src/systhread.c (sys_mutex_init, sys_mutex_lock, sys_mutex_unlock)
 (sys_mutex_destroy, sys_cond_init, sys_cond_wait)
 (sys_cond_signal, sys_cond_broadcast, sys_cond_destroy)
 (sys_thread_self, sys_thread_equal, w32_beginthread_wrapper)
 (sys_thread_create, sys_thread_yield) [WINDOWSNT]: New functions.

 configure.ac (THREADS_ENABLED): Enable threads for MinGW, even
 if pthreads is not available.

1 files changed, 34 insertions, 0 deletions

diff --git a/src/systhread.h b/src/systhread.h
index eb9cde78b61..52735449a5e 100644
--- a/src/systhread.h
+++ b/src/systhread.h
@@ -36,8 +36,42 @@ typedef pthread_t sys_thread_t;
 
 #else /* HAVE_PTHREAD */
 
+#ifdef WINDOWSNT
+
+/* This header is indirectly included in every source file.  We don't
+   want to include windows.h in every source file, so we repeat
+   declarations of the few necessary data types here (under different
+   names, to avoid conflicts with files that do include
+   windows.h).  */
+
+typedef struct {
+  struct _CRITICAL_SECTION_DEBUG *DebugInfo;
+  long LockCount;
+  long RecursionCount;
+  void *OwningThread;
+  void *LockSemaphore;
+  unsigned long SpinCount;
+} w32thread_critsect;
+
+enum { CONDV_SIGNAL = 0, CONDV_BROADCAST = 1, CONDV_MAX = 2 };
+
+typedef struct {
+  unsigned waiters_count;
+  w32thread_critsect waiters_count_lock;
+  void *events[CONDV_MAX];
+} w32thread_cond_t;
+
+typedef w32thread_critsect sys_mutex_t;
+
+typedef w32thread_cond_t sys_cond_t;
+
+typedef unsigned long sys_thread_t;
+
+#else  /* !WINDOWSNT */
+
 #error port me
 
+#endif  /* WINDOWSNT */
 #endif /* HAVE_PTHREAD */
 
 #else /* THREADS_ENABLED */