Parser doesn't recognize parameters added after first widget instantiated

[bill]

This is an edge case, but this doesn't work:

1. the parser parses a page with a ContentPane, thus caching the list of possible parameters for ContentPane:

   ...
   <div dojoType=dijit.layout.ContentPane>
   ...
   

2. after the parse, there's a dojo.require("dijit.layout.BorderContainer"), or TabContainer, etc, some class that adds new parameters to _Widget:

   dojo.extend(dijit._Widget, {
   	// region: [const] String
   	//		"top", "bottom", "leading", "trailing", "left", "right", "center".
   	//		See the BorderContainer description for details on this parameter.
   	region: '',
   ...
   });
   

3. parser is called again, to parse another ContentPane (inside a BorderContainer) that passes the new parameters like region:

   <div dojoType=dijit.layout.ContentPane region=top>
   

The parser won't pick up the region parameter and thus the BorderContainer won't layout correctly.

I think this actually might be a common case for dojox.layout.ContentPane, when the href-loaded content does dojo.require() calls.

I'll check in a test case along with the fix.

[bill]

(In [20112]) Widgets like BorderContainer? add properties to _Widget via dojo.extend(). If BorderContainer? is loaded after _Widget's parameter list has been cached, we need to refresh that cache (for _Widget and all widgets that extend _Widget).

Fixes #9897 !strict.

[bill]

(In [20615]) Use anonymous dojo.declare() rather than dojo.extend(), because dojo.extend() makes the parser flush it's cache. (And this particular dojo.extend() happens each time a Slider is instantiated.) Refs #9897 !strict.