* dev-threads merged to dev-img

* scanner generates only one file for image duplicates search
  (I will optimize this later... it has been disabled anyway)
* parallel imagesig analyser

(only tried to compile... not tested yet)

Merge with git+ssh://git.ucw.cz/projects/sherlock/GIT/sherlock.git#dev-threads

diff --cc lib/Makefile
Simple merge