Clean some CMake stuff in the extern directory

* Link GTK2 libraries instead of exporting it with the XXX_LIBRARIES
  variable
* Remove XXX_LINK_DIRECTORIES as we always export the full path of the
  library
* Export missing directory with XXX_INCLUDE_DIRS
* Link libraries using LINK_PRIVATE
* Add XXX_DEFINITIONS variables

Should fix some problems with the experimental build on the dashboard
and with YARP_USE_GTK2=ON when the goocanvasmm library is not
installed on the system
Fix previous commit 44af2e66
Link pango-cairo library to gybuilder

Should fix experimental builds on releases with DSO Linking
Do not include giomm include dirs as they are not needed

Should fix configure in experimental build on debian 6
Revert "Do not include giomm include dirs as they are not needed"

It breaks all the other builds.

This reverts commit db758d7fbf23e5ac4a0f2c4548c8e2c7a76bef6d.
fixing disapeared arrows in gyarpbuilder!
Fixed typos in gtkmm CMake variable name
yarprun: zombie hunter function has now its own thread (no more semaphore.wait() inside signal handler).
linux compilation fixes
use C++11 implementation of semaphore when YARP_EXPERIMENTAL_CXX11 is on
use C++11 implementation of threads when YARP_EXPERIMENTAL_CXX11 is on
prefer STL container classes when YARP_EXPERIMENTAL_CXX11 is on
fixed bug in xml file saving - did not report failure when write access was not granted
always initialize MultiNameSpace instances
begin clean-up of Protocol class, including removal of (long unused) IOException
more Protocol shuffling as prep for cleanup
testing new findgtk2
Do not build yarpview if CREATE_YARPVIEW is not defined
Some fix for YARP_USE_GTK2
Properly install CMake files

Foreach is not necessary, they can be intalled all at the same time