Upgrade to C++17

Change-Id: I0efd11f488ceee9b1a03ffaa1522cf0182ae1aca
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/configure.ac b/configure.ac
index b739d1e..a2ae7a6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -35,7 +35,7 @@
 PKG_INSTALLDIR
 
 # Checks for typedefs, structures, and compiler characteristics.
-AX_CXX_COMPILE_STDCXX([14], [noext], [mandatory])
+AX_CXX_COMPILE_STDCXX([17], [noext], [mandatory])
 AX_APPEND_COMPILE_FLAGS([-Wall -Wextra -Wpedantic], [CFLAGS])
 AX_APPEND_COMPILE_FLAGS([-Wall -Wextra -Wpedantic], [CXXFLAGS])