[autotools] Don't call CXX0X anymore.

It is gone in Dune's master. It is called by dune-common
anyway, like it's replacement CXX11.
(reviewed by bernd)


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@12820 2fb0f335-1f38-0410-981e-8018bf24f1b0

m4/cxx0x_constexpr.m4

 AC_DEFUN([CONSTEXPR_CHECK],[
   AC_REQUIRE([AC_PROG_CXX])
-  AC_REQUIRE([GXX0X])
   AC_LANG_PUSH([C++])
   AC_MSG_CHECKING([whether constexpr is supported])
   AC_COMPILE_IFELSE(