Backport change from 1.2.1: src/img.c: Only define INT32_T if it isn't already defined (it will be for 1.0.x).
git-svn-id: file:///home/survex-svn/survex/branches/1.0@3681 4b37db11-9a0c-4f06-9ece-9ab7cdaee568