Backport change from 1.2.0: configure.in,src/img.c,src/img.h: Sync latest versions of img.c and img.h from trunk, and configure code to define GETC and PUTC macros.
git-svn-id: file:///home/survex-svn/survex/branches/1.0@3677 4b37db11-9a0c-4f06-9ece-9ab7cdaee568