Import ThreadPool repository into log4cplus.
Update ThreadPool revision.
Improve .gitignore.
msttsappender.cxx: Avoid two uninitialized variables warning.
socket-unix.cxx: Initialize ghbn_mutex early.
thread_test/main.cxx: Fix formatting.
Do not test for C99 and GNU style variadic macros.

C++11 supports C99 variadic macros.
Do not check for GCC's __sync_*_and_fetch() built-ins.

We use C++11 atomics exclusively now.
Assume C++11 atomics and threads. Remove checks.
Update ThreadPool.
Add .rc file to include DLL version information on Windows
AUTHORS: Mention Oskari Timperi.
Move Win32-specific code under corresponding #ifdef
Remove unused typedef