Add StringMatcher#toString(); useful from a debugger.

src/main/java/org/apache/commons/lang3/text/StrMatcher.java

@@ -374,6 +374,12 @@ public int isMatch(final char[] buffer, int pos, final int bufferStart, final in
             }
             return len;
         }
+        
+        @Override
+        public String toString() {
+            return super.toString() + ' ' + Arrays.toString(chars);
+        }
+
     }
 
     //-----------------------------------------------------------------------