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.

regenerated the icons and logo from the svg file.

to 1 it automatically disables use of the bias since that is almost certainly
what the user will want to do.

instead of rolling its own implementation.

icon files.

avoid some silly warnings from gcc 4.4 and 4.5.

unlock a dlib::mutex it doesn't own.  This is technically a non-backwards
compatible change to the API but it has always been implemented in a way that
didn't allow this kind of double unlock() on non-Windows platforms.
Additionally, the recent change to the dlib::mutex implementation on windows
also no longer allows this kind of double unlock.

instead of mutex::unlock().