mutt stable branch with some hacks

Update UPDATING file for 1.13.3 release.

+4
+4
UPDATING
··· 8 8 The keys used are: 9 9 !: modified feature, -: deleted feature, +: new feature 10 10 11 + 1.13.3 (2020-01-12): 12 + 13 + ! Bug fix release. 14 + 11 15 1.13.2 (2019-12-18): 12 16 13 17 ! Bug fix release.