Interface Kit: Adjust max size and default alignment...

...on controls where it makes sense:
- BRadioButton and BCheckBox now return their preferred size as their
maximum.
- BRadioButton, BCheckBox and BTextControl now use left alignment by
default, as this is the most common use case for them.

headers/os/interface/TextControl.h

@@ -86,6 +86,7 @@ public:
 	virtual	BSize				MinSize();
 	virtual	BSize				MaxSize();
 	virtual	BSize				PreferredSize();
+	virtual	BAlignment			LayoutAlignment();
 
 			BLayoutItem*		CreateLabelLayoutItem();
 			BLayoutItem*		CreateTextViewLayoutItem();