LINT: add clang-tidy step (#6295)

* Implement new travis clang-tidy build step

* This step enable some rules and enforce one rule as error
* This permits to have some C++ quality rules based on clang & clang contributor guidelines

* Fix clang-tidy reported problems on push_back -> emplace_back

util/travis/script.sh

@@ -5,7 +5,7 @@
 needs_compile || exit 0
 
 if [[ "$LINT" == "1" ]]; then
-	# Lint with exit CI
+	# Lint and exit CI
 	perform_lint
 	exit 0
 fi