Boost.ASIO should not use compiler-based TLS unless it is allowed by the user of Boost.Log, otherwise the Boost.Log config option has no practical effect.
As a result, it becomes more probable that Boost.ASIO will be compiled with different config macros in Boost.Log and user's code. As a partial solution use
hidden visibility when building Boost.Log shared libs and ensure it uses its local copy of Boost.ASIO. Added a config test to detect support for visibility
command line option.
Also adjusted project names of other config tests to avoid possible name clashes with other libraries and Boost.Build infrastructure.
MSVC warning 4003 is now silenced on all compiler versions as apparently not only MSVC 8 is affected.
