Allow use of C++ 17

This should be fine to do now.

CMakeLists.txt

@@ -104,7 +104,7 @@ endif()
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${FLAGS_COMMON} -Wstrict-prototypes -std=gnu11")
 # Define __STDC_LIMIT_MACROS so |#include <stdint.h>| works as expected.
 # Define __STDC_FORMAT_MACROS so |#include <inttypes.h>| works as expected.
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${FLAGS_COMMON} -D__STDC_LIMIT_MACROS -D__STDC_FORMAT_MACROS -std=c++14")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${FLAGS_COMMON} -D__STDC_LIMIT_MACROS -D__STDC_FORMAT_MACROS -std=c++17")
 
 # We support three build types:
 # DEBUG: suitable for debugging rr