Make -Ox the default

Make -Ox the default; it's the optimization level expected by most
users, and it is clearly still causing confusion that it has to be
specified manually.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/doc/changes.src b/doc/changes.src
index e64aae7..9cd4b31 100644
--- a/doc/changes.src
+++ b/doc/changes.src
@@ -50,6 +50,9 @@
 
 \b Tighten EA checks. We warn a user if there overflow in EA addressing.
 
+\b Make \c{-Ox} the default optimization level.  For the legacy
+  behavior, specify \c{-O0} explicitly.  See \k{opt-O}.
+
 
 \S{cl-2.08} Version 2.08