Bugfix: Correctly free old assignments when reloading

Fixes #516

src/regex.c

@@ -49,6 +49,18 @@ struct regex *regex_new(const char *pattern) {
     return re;
 }
 
+/*
+ * Frees the given regular expression. It must not be used afterwards!
+ *
+ */
+void regex_free(struct regex *regex) {
+    if (!regex)
+        return;
+    FREE(regex->pattern);
+    FREE(regex->regex);
+    FREE(regex->extra);
+}
+
 /*
  * Checks if the given regular expression matches the given input and returns
  * true if it does. In either case, it logs the outcome using LOG(), so it will