Check if a token is inside of an isset(), empty() or array_key_exists() statement.

@since 0.5.0
@since 2.1.0 Now checks for the token being used as the array parameter
in function calls to array_key_exists() and key_exists() as well.

@param int $stackPtr The index of the token in the stack.

@return bool Whether the token is inside an isset() or empty() statement.