Slackware os and os_version explorer support.

cdist/conf/explorer/os

@@ -88,6 +88,11 @@ if [ -f /etc/SuSE-release ]; then
    exit 0
 fi
 
+if [ -f /etc/slackware-version ]; then
+   echo slackware
+   exit 0
+fi
+
 uname_s="$(uname -s)"
 
 # Assume there is no tr on the client -> do lower case ourselves

cdist/conf/explorer/os_version

@@ -54,6 +54,9 @@ case "$($__explorer/os)" in
    redhat|centos)
       cat /etc/redhat-release
    ;;
+   slackware)
+      cat /etc/slackware-version
+   ;;
    suse)
       cat /etc/SuSE-release
    ;;