CMake build scripts improved to simplify configuring and building of
project and tests.
Better use of compile definitions by replacing add_definitions with
target_compile_definitions. Use INTERFACE, PUBLIC and PRIVATE keywords
to separate scope of TORRENT_BUILDING_SHARED and TORRENT_LINKING_SHARED
definitions.
* Move tests to the separate file - test/CmakeLists.txt
* Fix use of compile definitions
* Remove redundant tailqueue.cpp
d-komarov