RFA: PATCH to use -std=c++98 in stage 1 of bootstrap

[Jason Merrill <jason@redhat.com>]

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I want to explicitly pass -std=c++98 to the compiler used in building 
stage 1.  Does this seem like the right way to do that?

Tested x86_64-pc-linux-gnu.

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commit 97e77ef17e558cdb6d26d440e691fea710e2a2dc
Author: Jason Merrill <jason@redhat.com>
Date:   Mon May 18 23:58:41 2015 -0400

    	* configure.ac: Add -std=c++98 to stage1_cxxflags.
    	* Makefile.in (STAGE1_CXXFLAGS): And substitute it.
    	* configure: Regenerate.

diff --git a/Makefile.in b/Makefile.in
index c221a0b..c59671a 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -489,6 +489,7 @@ STAGEfeedback_CONFIGURE_FLAGS = $(STAGE_CONFIGURE_FLAGS)
 # overrideable (for a bootstrap build stage1 also builds gcc.info).
 
 STAGE1_CFLAGS = @stage1_cflags@
+STAGE1_CXXFLAGS = @stage1_cxxflags@
 STAGE1_CHECKING = @stage1_checking@
 STAGE1_LANGUAGES = @stage1_languages@
 # * We force-disable intermodule optimizations, even if
diff --git a/configure b/configure
index d804329..37079fb 100755
--- a/configure
+++ b/configure
@@ -559,6 +559,7 @@ compare_exclusions
 host_shared
 stage2_werror_flag
 stage1_checking
+stage1_cxxflags
 stage1_cflags
 MAINT
 MAINTAINER_MODE_FALSE
@@ -14755,6 +14756,13 @@ case $build in
       *) stage1_cflags="-g -J" ;;
     esac ;;
 esac
+stage1_cxxflags="$stage1_cflags"
+if test "$GCC" = yes; then
+  # Build stage 1 in C++98 mode to ensure that a C++98 compiler can still
+  # start the bootstrap.
+  stage1_cxxflags="$stage1_cxxflags -std=c++98"
+fi
+
 
 
 
diff --git a/configure.ac b/configure.ac
index 4da04b7..2bf3245 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3476,8 +3476,15 @@ case $build in
       *) stage1_cflags="-g -J" ;;
     esac ;;
 esac
+stage1_cxxflags="$stage1_cflags"
+if test "$GCC" = yes; then
+  # Build stage 1 in C++98 mode to ensure that a C++98 compiler can still
+  # start the bootstrap.
+  stage1_cxxflags="$stage1_cxxflags -std=c++98"
+fi
 
 AC_SUBST(stage1_cflags)
+AC_SUBST(stage1_cxxflags)
 
 # Enable --enable-checking in stage1 of the compiler.
 AC_ARG_ENABLE(stage1-checking,