* src/threads/posix/thread-posix.cpp, src/threads/thread.cpp,

* src/threads/posix/thread-posix.cpp, src/threads/thread.cpp,
src/threads/thread.hpp: Factored out the implementation-specific bits.
* src/threads/thread-classpath.cpp, src/threads/thread-classpath.hpp
(ThreadRuntimeClasspath): GNU classpath implementation.
* src/threads/thread-cldc11.cpp, src/threads/thread-cldc11.hpp
(ThreadRuntimeCldc11): (Very) incomplete CLDC 1.1 implementation.
* src/threads/thread-openjdk.cpp, src/threads/thread-openjdk.hpp
(ThreadRuntimeOpenjdk): OpenJDK implementation.
* src/threads/Makefile.am: Added the new files.