fix indentation
Use condition variables instead of semaphores. Mac & Linux now
use the same synchronization code. Also fixes possible issues on
Mac with global semaphores not being cleaned up if program exits
abormally.
Set minimum stack size for threads on Linux/Mac (fixes crash bug in
deep searches on Mac OS, which has a 512k default stack limit for
threads created with pthread_create).
book updates (B92, C67)
update changelog
update makebook description, extensions & q-search description
fix friend declaration
book update (D44)