Modify INTEGER! multiplication to not use division for overflow detection.

Also, the modified multiplication does not use *undefined arithmetic*.
Modify INTEGER! addition and subtraction to not use *undefined arithmetic* and optimize.
Modify INTEGER! comparison to not use *undefined arithmetic* - fix [bug#2054](http://issue.cc/r3/2054)
Do not use MAX_NEG_INT (problematic name).
Amend a comment referring to reb-config.h
Tests in Linux (0.4.4) reveal 13 progressions and no regression
Multiplication speed tests reveal improvement