[PATCH] Cast markstack values to I32

The attached patch adds a couple of (I32) casts to MARK and
MARKSTACK operations, that all deal with pointer differences,
but assign the results to I32 variables.

Cheers,
-Jan

• [PATCH] Cast markstack values to I32 by Jan Dubois
• Re: [PATCH] Cast markstack values to I32 by Steve Peters