Upgrade liblouis to 2.6.0.

tools/checklicenses/checklicenses.py

Index: tools/checklicenses/checklicenses.py
diff --git a/tools/checklicenses/checklicenses.py b/tools/checklicenses/checklicenses.py
index ec775ebb7ee1cc6824480e607df5e532e532034b..338e4023246fea2693115441cd951a909df504fb 100755
--- a/tools/checklicenses/checklicenses.py
+++ b/tools/checklicenses/checklicenses.py
@@ -231,6 +231,16 @@ PATH_SPECIFIC_WHITELISTED_LICENSES = {
     'third_party/libjpeg_turbo': [  # http://crbug.com/98314
         'UNKNOWN',
     ],
+
+    # Many liblouis files are mirrored but not used in the NaCl module.
+    # They are not excluded from the mirror because of lack of infrastructure
+    # support.  Getting license headers added to the files where missing is
+    # tracked in https://github.com/liblouis/liblouis/issues/22.
+    'third_party/liblouis/src': [
+        'GPL (v3 or later)',
+        'UNKNOWN',
+    ],
+
     'third_party/libpng': [  # http://crbug.com/98318
         'UNKNOWN',
     ],