move lyndon_word.py file into words directory

src/sage/combinat/all.py

@@ -129,7 +129,6 @@
 from subset import Subsets
 #from subsets_pairwise import PairwiseCompatibleSubsets
 from necklace import Necklaces
-from lyndon_word import LyndonWord, LyndonWords, StandardBracketedLyndonWords
 from dyck_word import DyckWords, DyckWord
 from sloane_functions import sloane
 

src/sage/combinat/words/all.py

@@ -2,6 +2,7 @@
 Word features that are imported by default in the interpreter namespace
 """
 from alphabet import Alphabet, build_alphabet
+from lyndon_word import LyndonWord, LyndonWords, StandardBracketedLyndonWords
 from morphism import WordMorphism
 from paths import WordPaths
 from word import Word