lerpColor: round float to int instead of truncate.

It is done to match latest processing change: https://github.com/processing/processing/pull/2813
The lerp.pde test is updated with values computed with latest processing.
Just a lil' note: arithimetic operators got higher precedence over the other binary 1s.  
So parens can be removed: `x+.5 | 0`.  :P