Fixed an issue with slackpkg-2.83.0-noarch-3 (current-15/06/2018)

ap/slackpkg-2.83.0-noarch-3.txz:  Rebuilt.
  Don't remove ChangeLog.txt upon upgrade/reinstall.
  Use CHECKSUMS.md5.asc to determine if ChangeLog.txt is unchanged.

it downloads CHECKSUMS.md5.asc BEFORE ChangeLog.txt.
This broke the 'slackpkg update' in slackpkg+

Solved by force to download ChangeLog.txt the first time that
checkchangelog() ask for CHECKSUMS.md5.asc

src/slackpkgplus.sh

@@ -472,10 +472,23 @@ if [ "$SLACKPKGPLUS" = "on" ];then
     # The new getfile() download all file needed from all defined repositories
     # then merge all in a format slackpkg-compatible
   function getfile(){
+    if [ "$DOWNLOADCHANGELOG" = "force" -a $(basename $1) = "CHECKSUMS.md5.asc" ];then
+      echo "force to download ChangeLog"
+      DOWNLOADCHANGELOG=no
+      getfile "$(echo "$1"|sed 's/CHECKSUMS.md5.asc$/ChangeLog.txt/')" "$(echo "$2"|sed 's/CHECKSUMS.md5.asc$/ChangeLog.txt/')"
+      >$TMPDIR/changelogdownloaded
+      echo "PGP" >$TMPDIR/CHECKSUMS.md5.asc
+      return
+    fi
     local URLFILE
     URLFILE=$1
 
     if [ $(basename $1) = "ChangeLog.txt" ];then
+      if [ -e $TMPDIR/changelogdownloaded ];then
+	echo "                Done."
+	return
+      fi
+      rm -f $TMPDIR/CHECKSUMS.md5.asc
       echo "                ChangeLogs"
     fi
 
@@ -1599,6 +1612,7 @@ if [ "$SLACKPKGPLUS" = "on" ];then
     # answer to "Do you really want to download all other files"
     # if there are new changes
     ANSWER="Y"
+    DOWNLOADCHANGELOG=force
   fi
 
   if [ "$UPARG" != "gpg" ]&&[ "$CHECKGPG" = "on" ]&& ! ls -l $WORKDIR/gpg/GPG-KEY-slackware*.gpg >/dev/null 2>&1;then