Add Qt 5.1.1 and its SDK

Consider this as a first step towards the integration of Qt5 into nixpkgs,
it does not yet intends to replace Qt4 on every packages even if possible.
My goal here is to have a first derivation in common between people who
needs qt5 for development purposes.

The derivation has been written from scratch but I took care to read at the
version 4 to re-integrate some patches which are still compatible. However,
I did not had enough time to test gtkStyle and flashplayerFix as I do not
use any of them. Also, OSX users will have to do some extra work because
I do not have any mac.

Finally, as some configure flags have changed and in an hope to provide a
clear package definition before it becomes mature, I voluntary added some
flags which are default. Once every option will be mastered, we will just
have to redo a pass on qt5 configure flags and remove the ones which are
set by default.