Drop unneeded C++ compiler flag additions to AM_CXXFLAGS. Re #92

The AX_CXX_COMPILE_STDCXX_11 macro takes care of doing so if needed
already.

acinclude.m4

@@ -58,17 +58,6 @@ if test "${ac_cv_c_compiler_gnu}" = "yes"; then
 fi # ac_cv_c_compiler_gnu
 ])
 
-# SANE_SET_AM_CXXFLAGS()
-# Set default AM_CXXFLAGS.
-AC_DEFUN([SANE_SET_AM_CXXFLAGS],
-[
-AX_CXX_COMPILE_STDCXX_11([noext], [optional])
-if test "${ac_cv_cxx_compiler_gnu}" = "yes" -a "${ax_cv_cxx_compile_cxx11}" = "yes"; then
-  AM_CXXFLAGS="$AM_CXXFLAGS -std=c++11"
-fi # ac_cv_cxx_compiler_gnu
-])
-
-
 dnl SANE_CHECK_MISSING_HEADERS
 dnl Do some sanity checks. It doesn't make sense to proceed if those headers
 dnl aren't present.

configure.ac

@@ -81,7 +81,7 @@ dnl ***********************************************************************
 dnl set compiler/linker flags
 dnl ***********************************************************************
 SANE_SET_AM_CFLAGS([$is_release])
-SANE_SET_AM_CXXFLAGS
+AX_CXX_COMPILE_STDCXX_11([noext], [optional])
 SANE_SET_AM_LDFLAGS
 
 dnl ***********************************************************************