first experiments with blocked arrays
first version using sparse files (both on Windows and Linux)
introduced BlockedArrayTmpFile and enabled use of non-sparse files on Mac
first thread safe version (must be refactored and ported to Linux)
added atomic.hxx
renamed atomic.hxx => threading.hxx and added std::mutex and std::thread to vigra::threading namespace
first truly thread-safe version (need more testing!)
renamed block => chunk (Stuart's suggestion)
gcc compatibility fixes
refactoring (created test_chunked.cxx) and benchmarking
gcc compatibility fixes
added results of Linux benchmark
threading.hxx: Add preprocessor check for clang support of std threading.
test_chunked: Added missing 'template' keyword when calling get<>()
Merge pull request #169 from stuarteberg/blocked-iterator-mac-fixes

Blocked iterator mac fixes
fixed file resize for VIGRA_NO_SPARSE_FILE
added multi-threaded test for ChunkedArrayTmpFile
cmake: added compiler flags to run the multi-threaded chunked array test
restored test/multiarray/test.cxx (chunked tests are now in test/multiarray/test_chunked.cxx)
cmake: don't specify additional gcc flags when MSVC is used