Warn about precedence of metadata over binary operators

[serjek]

Consider example:

@:constant var timeOffset:Float = @byDefault Date.now().getTimezoneOffset()/(-60);

If overriden during model init this will give a warning
... has extra field timeOffset

Real problem is the precedence of metadata over binary operators, which is fixed by wrapping data:

@:constant var timeOffset:Float = @byDefault (Date.now().getTimezoneOffset()/(-60));

Coconut should give a warning when metadata is detected with binary operators.