[Users] Lost maximise / minimise / close icons in top RH corner

[Cliff Laine]

Just that really -- I'm not sure what I've done, but the little minus
sign, the plus sign, and the x in the top right of the main window have
disappeared, and CM now opens maximised, obscuring my taskbar (or
whatever the panel at the bottom of the window is called). The version
number at the top has also disppeared.

It's specific to CM -- the icons are there in Firefox and other
programs.

CM 3.14.1, Mint 18, Cinnamon, 32-bit

Cliff