Persistent AST and google sparsehash

[David Nolden]

For my teamwork-plugin I am using the boost serialization-library for 
serializing classes over the network.
See http://www.boost.org/libs/serialization/doc/index.html
and https://svn.kde.org/home/kde/branches/work/kdevelop-teamwork/kdevelop for 
how I use it.

It can be used to serialize any data-type, even smart-pointers or normal 
pointers(including tracking, which makes sure that pointers pointing to the 
same object still point to the same recreated object after deserialization).

And since the boost serialization-library may become a dependency of 
kdevelop-4 anyway because of my plugin, you may think about using it for 
AST-Persistence too.

greetings, David