Markup fixes.

Markup fixes.

        * gdk-pixbuf/tmpl/creating.sgml,
        gdk-pixbuf/tmpl/gdk-pixbuf-xlib-from-drawables.sgml,
        gdk-pixbuf/tmpl/gdk-pixbuf-xlib-init.sgml,
        gdk-pixbuf/tmpl/gdk-pixbuf-xlib-rendering.sgml,
        gdk-pixbuf/tmpl/refcounting.sgml: Markup fixes.

        * gtk/building.sgml, gtk/resources.sgml: Markup fixes.

        * gtk/gtk.types: Remove gtk_text_layout_get_type(). (???)

        * gdk/tmpl/general.sgml: Use <envar>, not <envvar>.

        * gdk-pixbuf-io.c, gdk-pixbuf-animation.c, gdk-pixbuf-data.c,
        gdk-pixbuf-loader.c, gdk-pixbuf-scale.c, gdk-pixbuf-util.c,
        gdk-pixdata.c: Markup fixes.