Update ax_boost_system.m4 to d48ec2210047bbf17702700811c3f16a5369e06c

configure

@@ -5101,7 +5101,7 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
 int
 main ()
 {
-boost::system::system_category
+boost::system::error_category *a = 0;
   ;
   return 0;
 }

m4/ax_boost_system.m4

@@ -31,7 +31,7 @@
 #   and this notice are preserved. This file is offered as-is, without any
 #   warranty.
 
-#serial 17
+#serial 18
 
 AC_DEFUN([AX_BOOST_SYSTEM],
 [
@@ -68,9 +68,10 @@ AC_DEFUN([AX_BOOST_SYSTEM],
 					   ax_cv_boost_system,
         [AC_LANG_PUSH([C++])
 			 CXXFLAGS_SAVE=$CXXFLAGS
+			 CXXFLAGS=
 
 			 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[@%:@include <boost/system/error_code.hpp>]],
-                                   [[boost::system::system_category]])],
+				    [[boost::system::error_category *a = 0;]])],
                    ax_cv_boost_system=yes, ax_cv_boost_system=no)
 			 CXXFLAGS=$CXXFLAGS_SAVE
              AC_LANG_POP([C++])