build: migrate to C++17

Change-Id: Ic66b1703fc7d1d51d61c442de859e0921c0bdd7a
diff --git a/.jenkins.d/40-headers-check.sh b/.jenkins.d/40-headers-check.sh
index da13efa..ad23cee 100755
--- a/.jenkins.d/40-headers-check.sh
+++ b/.jenkins.d/40-headers-check.sh
@@ -18,7 +18,7 @@
 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