SF bug #795506:  Wrong handling of string format code for float values.

Adding missing support for '%F'.

Will backport to 2.3.1.
diff --git a/Misc/NEWS b/Misc/NEWS
index cc2b858..a132b13 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
 Core and builtins
 -----------------
 
+- The % formatting operator now supports '%F' which is equivalent to
+  '%f'.  This has always been documented but never implemented.
+
 - complex(obj) could leak a little memory if obj wasn't a string or
   number.