try to remove bashsisms from postinst script

debian/alternc-slave.lintian

@@ -25,5 +25,3 @@ alternc-slave: executable-is-not-world-readable usr/lib/alternc/spoolsize.php 07
 alternc-slave: executable-is-not-world-readable usr/lib/alternc/sqlbackup.sh 0750 != 0755
 alternc-slave: executable-is-not-world-readable usr/lib/alternc/update_domains.sh 0750 != 0755
 alternc-slave: non-standard-dir-in-var var/backups/
-alternc-slave: possible-bashism-in-maintainer-script postinst:11 '    local question='
-alternc-slave: possible-bashism-in-maintainer-script postinst:12 '    local var='

debian/alternc-slave.postinst

@@ -8,8 +8,10 @@ set -e
 CONFIGFILE="/etc/alternc/local.sh"
 
 update_var() {
-    local question="$1"
-    local var="$2"
+    local question
+    local var
+    question="$1"
+    var="$2"
     db_get "$question"
     if [ ! -z "$RET" ]; then
         grep -Eq "^ *$var=" $CONFIGFILE || echo "$var=" >> $CONFIGFILE

debian/alternc.lintian

@@ -1,7 +1,6 @@
 alternc: non-standard-dir-in-var var/alternc/
 alternc: non-standard-dir-in-var var/backups/
 alternc: file-in-unusual-dir
-alternc: possible-bashism-in-maintainer-script
 alternc: setuid-binary usr/lib/alternc/mail_add 4750 root/www-data
 alternc: setuid-binary usr/lib/alternc/mail_del 4750 root/www-data
 alternc: setuid-binary usr/lib/alternc/quota_edit 4750 root/www-data

debian/alternc.postinst

@@ -8,8 +8,10 @@ set -e
 CONFIGFILE="/etc/alternc/local.sh"
 
 update_var() {
-    local question="$1"
-    local var="$2"
+    local question
+    local var
+    question="$1"
+    var="$2"
     db_get "$question"
     if [ ! -z "$RET" ]; then
         grep -Eq "^ *$var=" $CONFIGFILE || echo "$var=" >> $CONFIGFILE