Have ClassCollector ignore PHP 7 anonymous classes

Have ClassCollector ignore PHP 7 anonymous classes

PHP 7 introduces anonymous classes with a syntax like

 $instance = new class() extends Foo { ... };

ClassCollector is incorrectly detecting this as a class named
"() extends Foo". This patch fixes that by having it ignore "new class"
in much the same way it currently ignores "::class".

Change-Id: I4d1985a9c04be71f7bea6cb7b61dcea74f44a6e2