Made is_windows_rooted_path() able to cope with awkward but valid relative paths…

Made is_windows_rooted_path() able to cope with awkward but valid relative paths such as "C:..\File.txt".

Path "C:..\File.txt" refers to a file called File.txt located in the parent directory of the current directory on drive C:.

src/fileops.c

@@ -317,7 +317,7 @@ int gitfo_dirent(
 static int is_windows_rooted_path(const char* path)
 {
 	/* Does the root of the path look like a windows drive ? */
-	if (isalpha(path[0]) && (path[1] == ':') && (path[2] == '/'))
+	if (isalpha(path[0]) && (path[1] == ':'))
 		return GIT_SUCCESS;
 
 	return GIT_ERROR;