test of applying scr_hudscale to notifications

Cf. issue #6.

This seems to work (haven't tested much yet) but I'm dubious about it for a couple of reasons:
- If you get multiple notifications they can quickly eat up your screen.
- At hudscale 3, some notifications are too wide for the screen.

Maybe it would be preferable to have a separate scaling factor for notifications.
try using a separate scale factor for notify messages

Controlled by scr_notifscale. Can also be set through menu.
scr_notifscale -> scr_notifyscale
manage hudscale and notifyscale differently
Merge pull request #52 from SpiritQuaddicted/hudscale_notifies

optional scaling for notification messages