Constant folding

["Adam D. Moss" <adam@...>]

Mike Pall pointed out to me that the Lua 5.1 compiler
started to use constant folding optimizations at some
point in its development lifetime, which had somehow
escaped me previously.

Thanks to the Lua authors for that; e.g. now I can
write stuff like degrees-to-radians conversion in a
more obvious way, at least, without fear of wasting
VM instructions. :)

--adam