Add readability-redundant-* checks

There's a number of redundancies in our code that clang can sanitize
out.  Fix the existing problems, and enable the checks.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ie63d7b7f0777b702fbf1b23a24e1bed7b4f5183b
diff --git a/.clang-tidy b/.clang-tidy
index 953c78e..23cc7ae 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -276,6 +276,13 @@
 readability-else-after-return,
 readability-named-parameter,
 readability-redundant-control-flow,
+readability-redundant-declaration,
+readability-redundant-function-ptr-dereference,
+readability-redundant-member-init,
+readability-redundant-preprocessor,
+readability-redundant-smartptr-get,
+readability-redundant-string-cstr,
+readability-redundant-string-init,
 readability-identifier-naming'
 
 WarningsAsErrors: '*'