In configure, check for C++11
diff --git a/Makefile.in b/Makefile.in
index a0305da..2396714 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -193,6 +193,7 @@
 ECHO_N = @ECHO_N@
 ECHO_T = @ECHO_T@
 EXEEXT = @EXEEXT@
+HAVE_CXX11 = @HAVE_CXX11@
 INSTALL = @INSTALL@
 INSTALL_DATA = @INSTALL_DATA@
 INSTALL_PROGRAM = @INSTALL_PROGRAM@