Set sdbusplus to use c++17

C++17 is available with the current compiler. Changing to this standard
will allow sdbusplus to use some more advanced language features that
can reduce code size and improve readability.

Change-Id: Ia9a1af615bd5b3bc0868677308a8dd269a4bf5db
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>

configure.ac

@@ -70,7 +70,7 @@ AS_IF([test "x$enable_libsdbusplus" != "xno"],
 
 # Checks for typedefs, structures, and compiler characteristics.
 AS_IF([test "x$enable_libsdbusplus" != "xno"],
-      [AX_CXX_COMPILE_STDCXX_14([noext])])
+      [AX_CXX_COMPILE_STDCXX_17([noext])])
 AX_APPEND_COMPILE_FLAGS([-Wall -Werror], [CFLAGS])
 AX_APPEND_COMPILE_FLAGS([-Wall -Werror], [CXXFLAGS])