build: update to latest aur-fedora-mingw toolchain

Updated the NSis script to pick up the right libraries in the right
position.

Updated gschemas.compiled to gtk+ 3.12.0.
nodist: improve .gitignore

Inserted latex and latexmk generated files into .gitignore.
doc: update and corrected to latest gtk-doc
demo: improve user XP in cpml-demo

Use a vertical list instead of notebook labels to select the example to
be shown by cpml-demo. Added icons to that list to quickly identify the
items.
demo: merge gtk2/gtk3 versions of cpml-demo

The two sources differs only from how the cairo context is retrieved:
this is not enough to double the maintaining burden.
demo: avoid use of Gtk+2 specific properties in .ui
doc: use docbook tags instead of |[ ]|

The behavior of the above shortcuts has been modified, so using
docbook tags explicitely restore the old behavior.
doc: clean gtk-doc warnings

Updated docblocks to latest gtk-doc (1.20).
doc: correct gobject introspection annotations

Some annotation became deprecated and there was a missing colon in CPML.