doc: document operator and Dx changes

Document new operators, removal of special casing for %if, and the
MASM-like enhancements to the Dx directives.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
diff --git a/doc/changes.src b/doc/changes.src
index 85f3a9e..c1e7451 100644
--- a/doc/changes.src
+++ b/doc/changes.src
@@ -9,6 +9,16 @@
 
 \S{cl-2.15} Version 2.15
 
+\b The comparison and booleanizing operators can now be used in any
+expression context, not just \c{%if}. See \k{expr}.
+
+\b New operator \c{?} ... \c{:}.  See \k{exptri}.
+
+\b Signed shift operators \c{<<<} and \c{>>>}.  See \k{expshift}.
+
+\b The MASM \c{DUP} syntax for data definitions is now supported, in a
+somewhat enhanced form. See \k{db}.
+
 \b Warn for strange legacy behavior regarding empty arguments in
 multi-line macro expansion, but try to match legacy behavior in most
 cases. Legacy behavior can be disabled with the directive \c{%pragma