Named terminal symbols cannot be identifiers

[saschanaz]

interface interface {}; // shouldn't parse
enum enum {}; // shouldn't parse

interface _interface {}; // okay

Currently webidl2.js parses all string symbols as identifiers, instead it should distinguish named terminal symbols:

If the longest possible match could match one of the above named terminal symbols or one of the other terminal symbols from the grammar, it must be tokenized as the latter. Thus, the input text “long” is tokenized as the quoted terminal symbol long rather than an identifier called "long", and “.” is tokenized as the quoted terminal symbol . rather than an other.