m4 macro for checking whether cxx supports c++11

.gitignore

 build/
 autom4te.cache/
-m4/
 Makefile.in
 aclocal.m4
 ar-lib
@@ -16,3 +15,8 @@ install-sh
 ltmain.sh
 missing
 test-driver
+m4/libtool.m4
+m4/ltoptions.m4
+m4/ltsugar.m4
+m4/ltversion.m4
+m4/lt~obsolete.m4

configure.ac

@@ -15,8 +15,8 @@ AM_PROG_CC_C_O
 AC_PROG_CXX
 AC_PROG_INSTALL
 
-# check for C++14
-AX_CXX_COMPILE_STDCXX_14
+# check for C++11
+AX_CXX_COMPILE_STDCXX(11, noext, mandatory)
 
 # checks for libraires
 # pkg-config and libraries supporting that