Fix Lua operator overloading

Check for NaN rather than null since that's what parseFloat returns
when it fails (see https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/parseFloat#Description)
Fix os.time in lualib.js

os.time should return seconds, not milliseconds
Merge pull request #27 from elisee/master

Fix Lua operator overloading and os.time.
Fix math.random() to handle floats properly

Floats should be turned to integers in math.random().

For instance: math.random(0, 0.5) should always return 0.
Merge pull request #29 from elisee/randomfloat

Fix math.random() to handle floats properly
fix bug that does not allow semicolons after return or break statements
Merge branch 'master' into precompiled2
update luajs.zip