int patching

[Asko Kauppi <asko.kauppi@...>]

I found some more places (within 5.1w4) where integer optimizations 
were possible, s.a. for loop counters.  Performance on OSX is not much 
affected, and I haven't tested on ARM yet.

Also, I made a "fixed precision" patch (experimenting, it's fun! ;) 
which does not use any floating points internally (external interfaces 
kept as is).  The user (in 'luaconf.h') can define how much resolution 
is given to fractions, and how they are calculated (/10000, >>4 or 
such).  Seems handy, if assumptions on the numeric range can be made, 
of course.

-ak