re PR other/54324 (GCC install document does not list minimum required g++ version)

	PR other/54324
	* doc/install.texi (Tools/packages necessary for building GCC):
	Suggest --disable-stage1-checking for older GCC's.

From-SVN: r194586

gcc/ChangeLog

 2012-12-18  Aldy Hernandez  <aldyh@redhat.com>
 
 	PR other/54324
+	* doc/install.texi (Tools/packages necessary for building GCC):
+	Suggest --disable-stage1-checking for older GCC's.
+
+2012-12-18  Aldy Hernandez  <aldyh@redhat.com>
+
+	PR other/54324
 	* tree-ssa-coalesce.c (struct ssa_name_var_hash): Remove "union"
 	from template parameter.
 

gcc/doc/install.texi

@@ -254,6 +254,11 @@ To build all languages in a cross-compiler or other configuration where
 GCC binary (version 3.4 or later) because source code for language
 frontends other than C might use GCC extensions.
 
+Note that to bootstrap GCC with versions of GCC earlier than 3.4, you
+may need to use @option{--disable-stage1-checking}, though
+bootstrapping the compiler with such earlier compilers is strongly
+discouraged.
+
 @item GNAT
 
 In order to build the Ada compiler (GNAT) you must already have GNAT