Check bash version

MacOS ships an ancient bash version.

utils/dc

@@ -7,7 +7,13 @@
 # The latest version of this software should be available from my homepage:
 # http://www.pjcj.net
 
-set -euo pipefail
+if ((BASH_VERSINFO[0] < 5)); then
+  echo "❌ bash version $BASH_VERSION is too old. Please install v5 or higher."
+  exit 1
+fi
+
+set -eEuo pipefail
+shopt -s inherit_errexit
 
 script=$(basename "$0")
 readl=readlink