Add octal literals

This adds support for octal literals in the compiler.  Additionally, adds three passing tests: one for the most
common case, one that include the capital O version (0O instead of 0o), and one that checks a bad octal is
rejected.  It also adds a feature request for the ability to print formatted output with octals within it.

Somehow I'd missed that the C++ forums recommend strtoul, so I'll use that instead.