As you've seen it was fixed in MySQL 5.5.5, but MariaDB 5.1 (that's what you're using, right ?) is based MySQL 5.1.
Anyway, these are harmless warnings. If the compilation fails, please find a line with the real error that stops the compilation, and, I suppose, you'd better open a new bug report for it, and keep this one for %-style warnings.
No, it is not used.
As you've seen it was fixed in MySQL 5.5.5, but MariaDB 5.1 (that's what you're using, right ?) is based MySQL 5.1.
Anyway, these are harmless warnings. If the compilation fails, please find a line with the real error that stops the compilation, and, I suppose, you'd better open a new bug report for it, and keep this one for %-style warnings.