Prevent scanning classnames stored in string variables

[Starfox64]

Currently phpnsc will detect static calls over a classname stored in a string variable and report that the variable name is not a class in the namespace.

Example

static::$trackedClass::getFieldName($field);

example.php (1): Class trackedClass was referenced relatively but not defined

The edit to the static call Regex should prevent the scanning of classnames that start with a $