unicorn_load: Minor Windows-related changes

- Add missing include
- Fix a potential compilation issue where the constructor wouldn't be able to execute, as it would be private.

tests/A64/unicorn_emu/unicorn_load.cpp

@@ -9,8 +9,10 @@
 #include <unicorn/arm64.h>
 #include <unicorn_dynload.h>
 
+#include "common/assert.h"
+
 static struct LoadDll {
-private:
+public:
     LoadDll() {
         ASSERT(uc_dyn_load(NULL, 0));
     }