input: more debug messages
x11_common: deal with spurious LeaveNotify events

If the mpv window is unfocus, clicking on the OSC should focus the
window (done by the window manager) and allow interaction with the OSC.
But somehow X sends a spurious LeaveNotify event, immediately followed
by an EnterNotify event. This happens at least with IceWM. The result is
that the OSC will disappear (due to receiving MOUSE_LEAVE). The OSC will
stay invisible, because EnterNotify isn't handled, and there's nothing
that could make the OSC appear again.

Solve this by handling EnterNotify. We cause a redundant MOUSE_MOVE
event to be sent, which triggers the code to make the OSC visible. We
have to remove the code from input.c, which ignores redundant mouse move
events.

This also reverts commit 03fd2fe "input: Ignore spurious mouse moves".
input: allow window dragging even if mouse is in a mouse area

If the input section is enabled with MP_INPUT_ALLOW_VO_DRAGGING, then
the  VO will be allowed to drag the window with mouse button down +
mouse move even if the mouse is inside the section's mouse area.
lua part

see previous commit