phosphor-logging: use c++17

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

Change-Id: Ie34c3148c7f24f3b85931644da14bba93631d74a
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/configure.ac b/configure.ac
index ce9b8bb..fa1700a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -21,7 +21,7 @@
 AM_CONDITIONAL([INSTALL_SCRIPTS], [test "x$enable_install_scripts" = "xyes"])
 AS_IF([test "x$enable_install_scripts" != "xyes"], [
     # Checks for typedefs, structures, and compiler characteristics.
-    AX_CXX_COMPILE_STDCXX_14([noext])
+    AX_CXX_COMPILE_STDCXX_17([noext])
     AX_APPEND_COMPILE_FLAGS([-fpic -Wall -Werror], [CXXFLAGS])
 
     # Python