lint: Use c++17 std in cppcheck linter

test/lint/extended-lint-cppcheck.sh

@@ -66,7 +66,7 @@ function join_array {
 ENABLED_CHECKS_REGEXP=$(join_array "|" "${ENABLED_CHECKS[@]}")
 IGNORED_WARNINGS_REGEXP=$(join_array "|" "${IGNORED_WARNINGS[@]}")
 WARNINGS=$(git ls-files -- "*.cpp" "*.h" ":(exclude)src/leveldb/" ":(exclude)src/crc32c/" ":(exclude)src/secp256k1/" ":(exclude)src/univalue/" | \
-    xargs cppcheck --enable=all -j "$(getconf _NPROCESSORS_ONLN)" --language=c++ --std=c++11 --template=gcc -D__cplusplus -DCLIENT_VERSION_BUILD -DCLIENT_VERSION_IS_RELEASE -DCLIENT_VERSION_MAJOR -DCLIENT_VERSION_MINOR -DCOPYRIGHT_YEAR -DDEBUG -I src/ -q 2>&1 | sort -u | \
+    xargs cppcheck --enable=all -j "$(getconf _NPROCESSORS_ONLN)" --language=c++ --std=c++17 --template=gcc -D__cplusplus -DCLIENT_VERSION_BUILD -DCLIENT_VERSION_IS_RELEASE -DCLIENT_VERSION_MAJOR -DCLIENT_VERSION_MINOR -DCOPYRIGHT_YEAR -DDEBUG -I src/ -q 2>&1 | sort -u | \
     grep -E "${ENABLED_CHECKS_REGEXP}" | \
     grep -vE "${IGNORED_WARNINGS_REGEXP}")
 if [[ ${WARNINGS} != "" ]]; then