[PR][php-langspec][#114][PHP-5.6] - switch cannot contain arbitrary statements

You can view the Pull Request on github: https://github.com/php/php-langspec/pull/114 Pull Request Description: The definition of a switch statement was written too wage, incorrectly respectively: - a switch statement can only contain labeled-statement's and not arbitrary once - statements are optional in a switch statement - removed constrained for control expression (PHP does not force the expression to be a scalar: http://3v4l.org/3KZlG) - added constraint for case label expressions (maybe this was meant with control expression, anyway it was not correct entirely) (http://3v4l.org/lIMZJ / http://3v4l.org/5gDZM)