digikam from trunk : prepare to use an embedded dcraw binary version into digiKam

This is want mean that we can remove the external dcraw depency definitivly.
digiKAm will build and install a 'digikamdcraw' binary file witch can be used instead 'dcraw'

This way will solve all bug reported from users about uncompatible dcraw command options.
When we want to update dcraw in digiKam, we just need to update the dcraw.c and test the
compatibility with all options used by digiKAm core.

To digikam team : please let's me here if this way is right for you. Thanks in advance.