This puts the colours in inspect output and tracebacks back to what
they were in IPython 4.x, but leaves the prompt colouring as in 5.0.
I tried changing the colour scheme to 'Linux' entirely for Windows,
but that selects Monokai as the theme for prompt_toolkit, which looks
pretty horrible in 16 colours (at least to my eyes).
This is admittedly a hack, but hopefully our legacy colour system is
on the way out anyway.