linter 0.1.56


* fix to `avoid_positional_boolean_parameters` to ignore overridden methods
* fix to `prefer_is_empty` to not evaluate constants beyond int literals
* new lint: `null_closures`
* new lint: `lines_longer_than_80_chars`

Change-Id: Id11694d65091de6f26f521d62f3c5fb1921f58af
Reviewed-on: https://dart-review.googlesource.com/63271
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>
diff --git a/DEPS b/DEPS
index a5e2afb..a8e42cd 100644
--- a/DEPS
+++ b/DEPS
@@ -95,7 +95,7 @@
   "intl_tag": "0.15.2",
   "jinja2_rev": "2222b31554f03e62600cd7e383376a7c187967a1",
   "json_rpc_2_tag": "2.0.6",
-  "linter_tag": "0.1.55",
+  "linter_tag": "0.1.56",
   "logging_tag": "0.11.3+1",
   "markdown_tag": "2.0.0",
   "matcher_tag": "0.12.3",