raw2tiff: avoid divide by 0
fixes #151 (closed) / http://bugzilla.maptools.org/show_bug.cgi?id=2839
first memcmp() lines before computing correlation and always avoid divide by 0 anyway
fixes #151 (closed) / http://bugzilla.maptools.org/show_bug.cgi?id=2839
first memcmp() lines before computing correlation and always avoid divide by 0 anyway