To be sure that "in" is supported
I'd have to check for multiple possible
builtin attributes. Instead I do a try 
except.

- related cleanup

- fixed __ac_permissions__ created by the browser:view directive

- removed Five BrowserView as base class
(trying to move one more step forward instead of reverting revision 127298 and 127299 which did break CMF tests)

(Looks like someone mixed up zope.browserpage.metaconfigure.simple and zope.browserpage.simpleviewclass.simple. Doesn't make a big difference here, but zope.browserpage uses the other one in this place.)