Many changes to the C++ port.

Many changes to the C++ port.

- Refactoring:
 - All the files are now in a zxing folder,
 - Changed the namespaces so that everything is either in zxing or
zxing::qrcode.
 - Moved most function implementations from the headers to source
files.
- Ported the new design from the Java code with LuminanceSource,
BinaryBitmap, Binarizer, GlobalHistogramBinarizer and
LocalBlockBinarizer.
- Fixed two rare segmentation faults: one in
GridSampler::checkAndNudgePoints, and one in
ReedSolomonDecoder::decode. These would simply cause
ArrayIndexOutOfBoundsExceptions in Java, but have to be checked
explicitly in C++.
- With help from Erno Mäkinen, used std::vector instead of ArrayRef in
many places, as ArrayRef causes problems on Symbian phones.
- Added scons build files.
- Added a test application using ImageMagick.
- More small changes.

git-svn-id: http://zxing.googlecode.com/svn/trunk@1092 59b500cc-1b3d-0410-9834-0bbf25fbcc57