Switch to using WAPP_PLATFORM_CPP instead of __cplusplus

tests/cpath/test_cpath.h

@@ -3,16 +3,16 @@
 
 #include "wapp.h"
 
-#ifdef __cplusplus
+#ifdef WAPP_PLATFORM_CPP
 BEGIN_C_LINKAGE
-#endif // __cplusplus
+#endif // WAPP_PLATFORM_CPP
 
 TestFuncResult test_cpath_join_path(void);
 TestFuncResult test_cpath_dirname(void);
 TestFuncResult test_cpath_dirup(void);
 
-#ifdef __cplusplus
+#ifdef WAPP_PLATFORM_CPP
 END_C_LINKAGE
-#endif // __cplusplus
+#endif // WAPP_PLATFORM_CPP
 
 #endif // !TEST_CPATH_H