Merging in C++ classes and multithreaded support

Makefile.am

NEWS.txt

ax_pthread.m4

configure.ac

cppunit.m4

samples/Makefile.am

samples/callback-cpp-style.cpp

samples/callback-style.cpp

samples/posix-cpp-style.cpp

samples/posix-style.cpp

tests/Makefile.am

tests/fs_attrlist_apis.cpp

tests/fs_fname_apis.cpp

tests/fs_thread_test.cpp

tests/read_apis.cpp

tests/tsk_thread.cpp

tools/autotools/tsk_comparedir.cpp

tools/autotools/tsk_gettimes.cpp

tools/autotools/tsk_loaddb.cpp

tools/autotools/tsk_recover.cpp