phosphor-gpio-monitor: use c++17

Update configure.ac to choose the c++17 standard

Change-Id: Ie68586622ec8802ce1421dbbcfe8ec6a6f695df0
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/configure.ac b/configure.ac
index e331b8c..2217485 100644
--- a/configure.ac
+++ b/configure.ac
@@ -11,7 +11,7 @@
 AC_PROG_INSTALL
 
 # Checks for typedefs, structures, and compiler characteristics.
-AX_CXX_COMPILE_STDCXX_14([noext])
+AX_CXX_COMPILE_STDCXX_17([noext])
 AX_APPEND_COMPILE_FLAGS([-Wall -Werror], [CXXFLAGS])
 
 # For linking