vpx_thread: use CreateThread for windows phone

BUG=b/29583578

original webp change:

commit d2afe974f9d751de144ef09d31255aea13b442c0
Author: James Zern <jzern@google.com>
Date:   Mon Nov 23 20:41:26 2015 -0800

    thread: use CreateThread for windows phone

    _beginthreadex is unavailable for winrt/uwp

    Change-Id: Ie7412a568278ac67f0047f1764e2521193d74d4d

100644 blob 93f7622797f05f6acc1126e8296c481d276e4047 src/utils/thread.c
100644 blob 840831185502d42a3246e4b7ff870121c8064791 src/utils/thread.h

Change-Id: Iade8fff6367b45534986c77ebe61abeb45bce0f8

vpx_util/vpx_thread.h

@@ -45,6 +45,15 @@ typedef struct {
 } pthread_cond_t;
 #endif  // _WIN32_WINNT >= 0x600
 
+#ifndef WINAPI_FAMILY_PARTITION
+#define WINAPI_PARTITION_DESKTOP 1
+#define WINAPI_FAMILY_PARTITION(x) x
+#endif
+
+#if !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+#define USE_CREATE_THREAD
+#endif
+
 //------------------------------------------------------------------------------
 // simplistic pthread emulation layer
 
@@ -61,12 +70,21 @@ static INLINE int pthread_create(pthread_t* const thread, const void* attr,
                                  unsigned int (__stdcall *start)(void*),
                                  void* arg) {
   (void)attr;
+#ifdef USE_CREATE_THREAD
+  *thread = CreateThread(NULL,   /* lpThreadAttributes */
+                         0,      /* dwStackSize */
+                         start,
+                         arg,
+                         0,      /* dwStackSize */
+                         NULL);  /* lpThreadId */
+#else
   *thread = (pthread_t)_beginthreadex(NULL,   /* void *security */
                                       0,      /* unsigned stack_size */
                                       start,
                                       arg,
                                       0,      /* unsigned initflag */
                                       NULL);  /* unsigned *thrdaddr */
+#endif
   if (*thread == NULL) return 1;
   SetThreadPriority(*thread, THREAD_PRIORITY_ABOVE_NORMAL);
   return 0;