Use pattern.quote for safer quoting

Author: unp1

keyext.isabelletranslation/src/main/java/org/key_project/isabelletranslation/translation/ObserverFunctionHandler.java

@@ -35,7 +35,8 @@ public boolean canHandle(Operator op) {
     public StringBuilder handle(IsabelleMasterHandler trans, Term term) {
         if (trans.isNewSymbol(term)) {
             String opName = term.op().name().toString();
-            Matcher m = Pattern.compile("\\" + JavaDLFieldNames.IMPLICIT_NAME_PREFIX + "(.*?)")
+            Matcher m = Pattern
+                    .compile(Pattern.quote("\\" + JavaDLFieldNames.IMPLICIT_NAME_PREFIX) + "(.*?)")
                     .matcher(opName);
             String functionName;
             if (m.find()) {