Overly-generic syntax error messages

[jugglinmike]

JSHint reports certain syntax errors with generic messages for the following conditions:

• Constructors cannot be static methods
• Constructors cannot be generator methods
• Accessors cannot be generator methods
• Duplicate constructor definition
• super used outside of class literal
• super used outside of object literal

Unlike the majority of invalid syntax, these cases can be described concisely in plain English. Doing so may help users more quickly identify and correct their mistake.

To limit the profusion of error codes, consider which of these distinctions can be expressed through error message parameterization.

Edit: Some of those conditions do not need new messages. There is no restriction on static methods named "constructor", and we've recently fixed the way super is handled, including better messages.