Added Ok() member for print data, print dialog, page dialog, page dialog data

Added Ok() member for print data, print dialog, page dialog, page dialog data
so we can test in advance whether the print/page setup dialogs will fail.
Removed assertions that would fire if the default printer was not found, for example.
Added call to Ok() from HTML print code with suitable error message.
Commented out my erroneous fix to wxStaticText.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@15438 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775