[Ada] PR 22220

[Arnaud Charlet]

As mentioned under PR 22220, we now require GCC 4.0 or up to bootstrap
GNAT. Applied on trunk.

2010-06-23  Arnaud Charlet  <charlet@adacore.com

	PR 22220
	* doc/install.texi: Update requirements to build GNAT.

--
--- install.texi	(revision 160834)
+++ install.texi	(working copy)
@@ -2301,7 +2301,7 @@ and network filesystems.
 @section Building the Ada compiler
 
 In order to build GNAT, the Ada compiler, you need a working GNAT
-compiler (GCC version 3.4 or later).
+compiler (GCC version 4.0 or later).
 This includes GNAT tools such as @command{gnatmake} and
 @command{gnatlink}, since the Ada front end is written in Ada and
 uses some GNAT-specific extensions.