mdmg build of gtk2 does not include cairo

[Kevin Layer]

I'm happy to report with 1.9.2, I was able to build a 64-bit mdmg.
Below are the complete instructions, for the record.  I tested my app,
and it works fine.

# On a fully up-to-date 10.5 Intel system

# first, uninstall
port -f uninstall installed
rm -rf /opt/local \
    /Applications/DarwinPorts \
    /Applications/MacPorts \
    /Library/LaunchDaemons/org.macports.* \
    /Library/Receipts/DarwinPorts*.pkg \
    /Library/Receipts/MacPorts*.pkg \
    /Library/StartupItems/DarwinPortsStartup \
    /Library/Tcl/darwinports1.0 \
    /Library/Tcl/macports1.0 \
    ~/.macports

# Install MacPorts 1.9.2

# Edit /opt/local/etc/macports/macports.conf
#
#	build_arch	x86_64
#	universal_archs x86_64 i386 

# build
port install gtk2 +x11 configure.compiler=gcc-4.2
port mdmg gtk2 +x11 configure.compiler=gcc-4.2