clang-tidy cleanups (#800)

clang-tidy cleanups (#800)

* clang-tidy: use bool literals

Found with modernize-use-bool-literals

Signed-off-by: Rosen Penev <rosenp@gmail.com>
* clang-tidy: replace std::bind with lambdas

Found with modernize-avoid-bind

Signed-off-by: Rosen Penev <rosenp@gmail.com>
* clang-tidy: use data() instead of pointer stuff

Found with readability-container-data-pointe

Signed-off-by: Rosen Penev <rosenp@gmail.com>
* clang-tidy: use empty()

Found with readability-container-size-empty

Signed-off-by: Rosen Penev <rosenp@gmail.com>
* clang-tidy: remove static in anon namespace

Found with readability-static-definition-in-anonymous-namespace

Signed-off-by: Rosen Penev <rosenp@gmail.com>
* clang-tidy: remove const return

Found with readability-const-return-type

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Signed-off-by: Rosen Penev <rosenp@gmail.com>