significantly improved Isabelle/Isar implementation manual;

--- a/NEWS	Mon Oct 25 16:14:40 2010 +0200
+++ b/NEWS	Mon Oct 25 16:17:16 2010 +0200
@@ -6,6 +6,8 @@
 
 *** General ***
 
+* Significantly improved Isabelle/Isar implementation manual.
+
 * Explicit treatment of UTF8 sequences as Isabelle symbols, such that
 a Unicode character is treated as a single symbol, not a sequence of
 non-ASCII bytes as before.  Since Isabelle/ML string literals may