look at 64-bit warnings after changing to use off_t instead of size_t when using expressions with subtraction

To: http://www.spamgourmet.com/~home.robertwork
Subject: look at 64-bit warnings after changing to use off_t instead of size_t when using expressions with subtraction
From: http://dummy.us.eu.org/robert (Robert)
Date: Sun, 27 Dec 2015 18:51:12 -0800