CI/Circle CI: Enforce codestyle checks

(cherry picked from commit 32c9f1c7a228db33110ab0ab5975ba37cba85106)

contrib/check_codestyle.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+set -e
+
+echo "Codestyle check script:"
+echo
+
+regexChecks=()
+
+for check in ${regexChecks[@]}; do
+    echo "  Checking RegEx: '${check}'"
+    
+    if grep -E -r ${check} src; then
+        exit 1
+    fi
+done
+
+echo "Everything looks good"