chdir() => Change_directory()

improve portability

src/io.h

@@ -32,6 +32,7 @@
 /// - opendir()
 /// - readdir()
 /// - getcwd()
+/// - chdir()
 /// - Also, don't assume "/" or "\\", use PATH_SEPARATOR
 /// If you don't, you break another platform.
 //////////////////////////////////////////////////////////////////////////////
@@ -130,3 +131,7 @@ void Release_lock_file(const char *file_directory);
 ///
 /// Return the current directory, equivalent to getcwd()
 const char * Get_current_directory(char * buf, size_t size);
+
+///
+/// Change current directory. return 0 for success, -1 in case of error
+int Change_directory(const char * path);