A Lang supported by the application.
a valid ISO Language Code.
a valid ISO Country Code.
The Lang code (such as fr or en-US).
Whether this lang satisfies the given lang.
If the other lang defines a country code, then this is equivalent to equals, if it doesn't, then the equals is
only done on language and the country of this lang is ignored.
This implements the language matching specified by RFC2616 Section 14.4. Equality is case insensitive as per
The accepted language
Convert to a Java Locale value.