Reduce min angle for gfxsetdefaultfov, and add an easy control for it

pantagruel01

In costume contests, it would often be nice to zoom in on the winners. You can to a limited degree do this with /gfxsetdefaultfov, but it has a minimum angle of 16 (default 55), so you are capped at a bit over x3 magnification. Reduce the min angle to 6 and it's nearly x10, perfect as opera glasses.