Parser: allow overriding startup methods

[bill]

If function foo() is called by postCreate() etc., then you can define it like

<button dojoType=dijit.form.Button foo="...">

but can't define it like

<button dojoType=dijit.form.Button>
   <script type="dojo/method" event="foo">...

Allow this by changing parser to mixin foo into the parameters to the widget:

  new dijit.form.Button({foo: ...});

for both the first and second case (it's already done for the first case)

[bill]

(In [10399]) Fixes #4338: allow setting widget startup methods via <script type="dojo/method" event="foo">

[alex]

this change breaks dijit.Declaration's use of _wireUpMethod, meaning that the mail demo is b0rken as is the table demo in dojox.data. Reopening.

[bill]

(In [10406]) updates needed to Declaration due to changes to parser (refs #4338)