added missing functions to MessageDialog

[iK4tsu]

Signed-off-by: João Lourenço jlourenco5691@gmail.com

[ljmf00]

I would say it's better to put the function inside this file, here: https://github.com/gtkd-developers/GtkD/blob/master/src/APILookupGtk.txt#L2007

by adding:

noCode: format_secondary_text
noCode: format_secondary_markup

and the actual code inside this scope:

code: start
// ...
code: end

Anyway, I don't see any of these as a good approach since it should be generated from the bindings. Could you give a hint here @MikeWey ?

[MikeWey]

Adding them via the Lookup files is indeed better, since than the additions will survive when regenerating the binding.

The aren't generated because we currently don't have a good way to get the variatic parameter across the binding without human intervention. Although dlangs meta programming may have improved enough to get it working.

[iK4tsu]

Sorry I'm new to this project. I noticed those files before making the PR, but found it strange when some functions were missing, setMarkup and the deprecated getImage and setImage. Because of that I decided to add them directly on the class itself. Maybe I should've just made an issue instead. Since the PR I've been trying to figure out how to generate those bindings with the Lookup file, unsuccessfully.

Should I amend my PR and add these changes in the Lookup file? And how can I test it?