Fix a potential integer overflow
Fix a potential integer overflow

multiplication of two 32-bit integers will yield a 32-bit integer, and
that could overflow, even though it's gonna be stored in a 64-bit
integer. The overflow happens before widening.

zsx/r3,Pointillistic/rebol-lang,Pointillistic/rebol-lang,Pointillistic/rebol-lang,zsx/r3,zsx/r3,zsx/r3,Pointillistic/rebol-lang