Update build.yml for codespell, fix some spelling.

packaging: Forbid compilation if the symbols file is outdated

An outdated symbols file results in automatic versioned dependencies
in projects which use this library.

When these projects are built, shlibs:Depends cannot find a version
number for the set of symbols so it uses the full version of the
library package, including suffixes such as +virginia.

We end up with depends lib (>== 6.0.0+virginia) instead of
lib (>== 6.0.0).

xapp-gtk3-module.c: Use the 'realize' signal to trigger injecting

the favorites:https:// uri into the sidebar places.

It's not important where this occurs, but doing it during the
GtkPlacesSidebar constructed vfunc now causes a deadlock in the
dconf engine between the GSettings instance for favorites, and
the one for GtkFileChooserWidget settings, created during its
construction.

I've been unable to determine any particular commit that may be
to blame, between gtk, gio, meld and dconf, and I'm unable to
reproduce this anywhere but in Meld thus far.

The 'realize' signal is sent after widget construction so is
safely outside the template machinery.

Fixes linuxmint#171.