- introduction of a threadpool for crawling
- introduction of a job queue to avoid buzy waiting for a free crawler slot
*) New classes added
- queue for receiving of crawler jobs
- semaphore class to do reader/writer synchronization (mutual exclusion)
- message object to hold all needed data about a crawler job
*) Trying to solve session-thread shutdown problem
- session thread stopped variable is now set from outside before interrupting the
session thread.
git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@39 6c8d7289-2bf4-0310-a012-ef5d649a1542
