Only minor tweaking lead me really to the build of gtk! All dependencies are build - I'm happy! Patches are committed.

The library itself is compiled successfully, but then comes this the error message 8-( :
GDK_PIXBUF_MODULE_FILE=../gdk-pixbuf/gdk-pixbuf.loaders ./gtk-update-icon-cache --force --ignore-theme-index            
\
           --source builtin_icons stock-icons > gtkbuiltincache.h.tmp &&        \
        mv gtkbuiltincache.h.tmp gtkbuiltincache.h
GLib: Cannot convert message: Conversion from character set 'UTF-8' to 'C' is not supported
No theme index file in '--force'.
If you really want to create an icon cache here, use --ignore-theme-index.
gmake[2]: *** [gtkbuiltincache.h] Error 1
gmake[2]: Leaving directory `/usr/src/HEAD/pkgsrc/x11/gtk2/work/gtk+-2.12.0/gtk'


Here is the list of newly build and packaged packages:

libX11-1.1.3        Base X libraries from modular Xorg X11
fixesproto-4.0      Fixes extension headers from X.org
compositeproto-0.4  Composite extension headers from modular X.org
damageproto-1.1.0   Damage extension headers from modular X.org
evieext-1.0.2       EvIE extension headers
fontsproto-2.0.2    Fonts extension headers from X.org
randrproto-1.2.1    Randr extension headers from modular X.org
renderproto-0.9.2   Render extension headers from modular X.org
resourceproto-1.0.2 Resource extension headers from X.org
scrnsaverproto-1.1.0 ScrnSaver extension headers from X.org
libXext-1.0.3       X Extension library
libXi-1.1.3         X Input extension library
trapproto-3.4.3     Trap extension headers
videoproto-2.2.2    Video extension headers from modular X.org X11
xf86dgaproto-2.0.2  XF86DGA extension headers
glproto-1.4.8       GL extension headers
glib2-2.14.1        Some useful routines for C programming (glib2)
py-gobject-shared-2.12.3 Python bindings for glib2 gobject
xineramaproto-1.1.2 Xinerama extension headers from X.org
xdg-dirs-1.4        Shared XDG directories
libXfixes-4.0.3     Xfixes library and extension of X RandR from modular X.org
libXrender-0.9.2    X Render Library
libXcursor-1.1.8    Client-side cursor loading library for X
libXinerama-1.0.2   X PanoramiX extension library
libXrandr-1.2.2     X RandR Library from X.org
libICE-1.0.3        Inter Client Exchange (ICE) library for X
libSM-1.0.3         X Session Management Library
libXt-1.0.5         X Toolkit Intrinsics library
atk-1.20.0          Set of interfaces for accessibility
freetype2-2.3.5     Font rendering engine and library API
expat-2.0.1         XML parser library written in C
fontconfig-2.4.2nb3 Library for configuring and customizing font access
libXft-2.1.12       Library for configuring and customizing font access
makedepend-1.0.1    Dependency generator for make
MesaLib-6.4.2nb3    Graphics library similar to SGI's OpenGL
glitz-0.5.6nb2      OpenGL 2D graphics library and a backend for gl output in cairo
cairo-1.4.10        Vector graphics library with cross-device output support
pango-1.18.2        Library for layout and rendering of text