Fix fatal error when compiling for windows on dev

src/sync.cpp

@@ -25,9 +25,14 @@
 #include <boost/foreach.hpp>
 #include <boost/thread.hpp>
 
+#ifdef _WIN32
+#include <windows.h>
+#include <dbghelp.h>
+#else
 #include <execinfo.h> /* backtrace, backtrace_symbols_fd */
-#include <unistd.h> /* STDOUT_FILENO */
+#endif
 
+#include <unistd.h> /* STDOUT_FILENO */
 
 #ifdef DEBUG_LOCKCONTENTION
 void PrintLockContention(const char* pszName, const char* pszFile, int nLine)