Send correct position in ConfigureNotify events (FS#1030)

This event should contain the position of the top-left corner of the client's
content area. Thus, we have to add the border width to the position.

Signed-off-by: Uli Schlachter <psychon@znc.in>
Fix minor memory leak in mouse_query_pointer()

Signed-off-by: Uli Schlachter <psychon@znc.in>