Bump version
Drop markup from doc comments

Switch to markdown for our inline markup needs, and
turn off sgml mode for the docs.
Bump gtk-doc dep to 1.20
2.30.5
Bump version
Add annotations to gdk_pixbuf_save_to_buffer buffer arg
Don't Build Introspection Files from MSVC Projects

This removes the gengir projects from the Visual Studio Projects, so that
this paves the initial step of building the introspection files using NMake
Makefiles, as the current approach requires many environment variables to
be set in order to build the introspection files successfully, which is a
bit clunky.
MSVC builds: Add NMake Makefile for Introspection Builds

This adds an NMake Makefile that is used to generate the introspection
files for GDK-Pixbuf, which replaces the previous approach of generating
them via the Visual Studio Projects.  This makes it clearer to people on
what things are needed in order to build the introspection files if so
desired, and makes things a bit cleaner as the build results can be
cleaned away easily.  This also takes the recent change in g-i into
account, where we no longer pass in the DLL file name but instead pass in
the library name on Windows, just as it was done on *nix.

The existing .bat file for this purpose is removed as a result.