win32: assert when VLC_CANCEL_ADDR_SET has another address already set
win32: assert when VLC_CANCEL_ADDR_SET has another address already set

in par with the assert in VLC_CANCEL_ADDR_CLEAR but we can tell who's guilty

Signed-off-by: Rémi Denis-Courmont <f0699137713be92736351a0674e79536595e4a60@remlab.net>

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc