Merge pull request #1740 from rubenk/correct-am_cflags

Append -Werror to the right flags

diff --combined configure.ac
index eb5d17b,7aff89a..4816c75
--- 1/configure.ac
--- 2/configure.ac
+++ b/configure.ac
@@@ -800,14 -800,12 +800,14 @@@ AC_CHECK_FUNCS(gettimeofday select strd
  AC_FUNC_STRERROR_R
  
  test_cxx_flags() {
 -      AC_LANG_PUSH(C++)
 -      AC_LANG_CONFTEST([int main(void){}])
 +      AC_LANG_PUSH([C++])
 +      AC_LANG_CONFTEST([
 +              AC_LANG_SOURCE([[int main(void){}]])
 +      ])
        $CXX -c conftest.cpp $CXXFLAGS $@ > /dev/null 2> /dev/null
        ret=$?
        rm -f conftest.o
 -      AC_LANG_POP(C++)
 +      AC_LANG_POP([C++])
        return $ret
  }
  
@@@ -6201,7 -6199,7 +6201,7 @@@ AM_CXXFLAGS="-Wall
  if test "x$enable_werror" != "xno"
  then
          AM_CFLAGS="$AM_CFLAGS -Werror"
-         AM_CXXFLAGS="$AM_CFLAGS -Werror"
+         AM_CXXFLAGS="$AM_CXXFLAGS -Werror"
  fi
  AC_SUBST([AM_CFLAGS])
  AC_SUBST([AM_CXXFLAGS])