Also added the orthogonalize() function.

to get the Q matrix by reference rather than by value.

learn_platt_scaling(), that allows you to directly call the Platt scaling code
without supplying a trainer object.

which mouse button was double clicked.

image_window::get_next_double_click() was slightly off.

when set_image() is called with an image the same size as the one currently
being displayed.

or std::vector<unsigned char> were serialized.

clang and also fixed a function call ambiguity.

get information about where the user is clicking.

grayscale PNGs were used.  libpng doesn't automatically convert from host
endianness to big endian as the PNG standard demands.  You have to explicitly
tell it to do this or it will write out the 16bit pixel data in host order
which result in the wrong thing happening on little endian chips.  Similarly
for reading PNGs.

istream.  The bug caused the function to crash on strings longer than 56
characters.

calls.