RFA: mention gdb/gdbserver/README in gdb/README

[Jim Blandy]

Does this change look okay?

gdb/ChangeLog:
2008-01-16  Jim Blandy  <jimb@codesourcery.com>

	* README: Doc fix.

diff -r 79c1d0c9402b gdb/README
--- a/gdb/README	Tue Jan 15 10:14:02 2008 -0800
+++ b/gdb/README	Wed Jan 16 14:55:33 2008 -0800
@@ -453,6 +453,10 @@ allows remote debugging for Unix applica
 allows remote debugging for Unix applications.  gdbserver is only
 supported for some native configurations, including Sun 3, Sun 4, and
 Linux.
+The file gdb/gdbserver/README includes further notes on gdbserver; in
+particular, it explains how to build gdbserver for cross-debugging
+(where gdbserver runs on the target machine, which is of a different
+architecture than the host machine running GDB).
 
    There are a number of remote interfaces for talking to existing ROM
 monitors and other hardware: