include windows.h instead of synchapi.h for win32

the win32 API uses some architecture-specific defines, but they're not
defined by the MSVC compiler - they're defined directly in windows.h
based on symbols defined by the MSVC compiler. rather than setting the
architecture symbols ourselves, just import windows.h as a whole.

this also needed to disable the short-name symbols in cmark-gfm.h,
because there are some clashing symbols in win32 headers.

Author: QuietMisdreavus

src/include/cmark-gfm.h

@@ -807,7 +807,7 @@ const char *cmark_version_string(void);
  * John MacFarlane, Vicent Marti,  Kārlis Gaņģis, Nick Wellnhofer.
  */
 
-#ifndef CMARK_NO_SHORT_NAMES
+#if !defined(CMARK_NO_SHORT_NAMES) && !defined(_WIN32)
 #define NODE_DOCUMENT CMARK_NODE_DOCUMENT
 #define NODE_BLOCK_QUOTE CMARK_NODE_BLOCK_QUOTE
 #define NODE_LIST CMARK_NODE_LIST

src/include/mutex.h

@@ -31,7 +31,7 @@ pthread_mutex_lock(&NAME##_lock);
 #elif defined(_WIN32) // building for windows
 
 #define _WIN32_WINNT 0x0600
-#include <synchapi.h>
+#include <windows.h>
 
 #define CMARK_DEFINE_ONCE(NAME) static INIT_ONCE NAME##_once = INIT_ONCE_STATIC_INIT;