patch to fix "broken" mouse after exit

[Oskar Liljeblad <oskar osk mine nu>]

Hello,

When you exit mc the mouse is left enabled which means that it still
reports events to the terminal and cannot be used for marking text.

The attached patch fixes that. Although not required to fix the
problem, it also moves the call to disable_mouse from
layout.c:done_screen to main.c:done_mc. This is merely to create
better "symmetry" because enable_mouse (opposite to disable_mouse)
is called in setup_mc (opposite to done_mc).

Oskar Liljeblad (oskar osk mine nu)