Fix MSVC compilation warnings

tests/t00-core.c

@@ -502,27 +502,27 @@ static int setup_empty_tmp_dir()
 {
 	char path[GIT_PATH_MAX];
 
-	if (mkdir(empty_tmp_dir, 0755))
+	if (p_mkdir(empty_tmp_dir, 0755))
 		return -1;
 
 	git_path_join(path, empty_tmp_dir, "/one");
-	if (mkdir(path, 0755))
+	if (p_mkdir(path, 0755))
 		return -1;
 
 	git_path_join(path, empty_tmp_dir, "/one/two_one");
-	if (mkdir(path, 0755))
+	if (p_mkdir(path, 0755))
 		return -1;
 
 	git_path_join(path, empty_tmp_dir, "/one/two_two");
-	if (mkdir(path, 0755))
+	if (p_mkdir(path, 0755))
 		return -1;
 
 	git_path_join(path, empty_tmp_dir, "/one/two_two/three");
-	if (mkdir(path, 0755))
+	if (p_mkdir(path, 0755))
 		return -1;
 
 	git_path_join(path, empty_tmp_dir, "/two");
-	if (mkdir(path, 0755))
+	if (p_mkdir(path, 0755))
 		return -1;
 
 	return 0;