build: switch to C++17

Change-Id: I92039300ce845de0312dceccb94c128229ed60c4
diff --git a/.jenkins.d/40-headers-check.sh b/.jenkins.d/40-headers-check.sh
index 8ee3339..40e5f34 100755
--- a/.jenkins.d/40-headers-check.sh
+++ b/.jenkins.d/40-headers-check.sh
@@ -16,7 +16,7 @@
 fi
 
 CXX=${CXX:-g++}
-STD=-std=c++14
+STD=-std=c++17
 CXXFLAGS="-O2 -Wall -Wno-unneeded-internal-declaration -Wno-unused-const-variable $(pkg-config --cflags libndn-cxx $PCFILE)"
 INCLUDEDIR="$(pkg-config --variable=includedir $PCFILE)"/$PROJ