mention deprecation of ++/-- in the changelog.

Author: lattner

CHANGELOG.md

@@ -1,6 +1,10 @@
 Latest
 ------
 
+* The ++ and -- operators have been deprecated, and are slated to be removed in
+  Swift 3.0.  As a replacement, please use "x += 1" on integer or floating point
+  types, and "x = x.successor()" on Index types.
+
 * The operator identifier lexer grammar has been revised to simplify the rules
   for operators that start with a dot (".").  The new rule is that an operator
   that starts with a dot may contain other dots in it, but operators that start