Adding m4 macro for C++17

Author: andrewdavidsmith

m4/ax_cxx_compile_stdcxx_11.m4 m4/ax_cxx_compile_stdcxx_17.m4m4/ax_cxx_compile_stdcxx_11.m4 renamed to m4/ax_cxx_compile_stdcxx_17.m4

@@ -1,39 +1,35 @@
 # =============================================================================
-#  https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html
+#  https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_17.html
 # =============================================================================
 #
 # SYNOPSIS
 #
-#   AX_CXX_COMPILE_STDCXX_11([ext|noext], [mandatory|optional])
+#   AX_CXX_COMPILE_STDCXX_17([ext|noext], [mandatory|optional])
 #
 # DESCRIPTION
 #
-#   Check for baseline language coverage in the compiler for the C++11
+#   Check for baseline language coverage in the compiler for the C++17
 #   standard; if necessary, add switches to CXX and CXXCPP to enable
 #   support.
 #
 #   This macro is a convenience alias for calling the AX_CXX_COMPILE_STDCXX
-#   macro with the version set to C++11.  The two optional arguments are
+#   macro with the version set to C++17.  The two optional arguments are
 #   forwarded literally as the second and third argument respectively.
 #   Please see the documentation for the AX_CXX_COMPILE_STDCXX macro for
 #   more information.  If you want to use this macro, you also need to
 #   download the ax_cxx_compile_stdcxx.m4 file.
 #
 # LICENSE
 #
-#   Copyright (c) 2008 Benjamin Kosnik <[email protected]>
-#   Copyright (c) 2012 Zack Weinberg <[email protected]>
-#   Copyright (c) 2013 Roy Stogner <[email protected]>
-#   Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <[email protected]>
-#   Copyright (c) 2015 Paul Norman <[email protected]>
 #   Copyright (c) 2015 Moritz Klammler <[email protected]>
+#   Copyright (c) 2016 Krzesimir Nowak <[email protected]>
 #
 #   Copying and distribution of this file, with or without modification, are
 #   permitted in any medium without royalty provided the copyright notice
 #   and this notice are preserved. This file is offered as-is, without any
 #   warranty.
 
-#serial 18
+#serial 2
 
 AX_REQUIRE_DEFINED([AX_CXX_COMPILE_STDCXX])
-AC_DEFUN([AX_CXX_COMPILE_STDCXX_11], [AX_CXX_COMPILE_STDCXX([11], [$1], [$2])])
+AC_DEFUN([AX_CXX_COMPILE_STDCXX_17], [AX_CXX_COMPILE_STDCXX([17], [$1], [$2])])