better col_offsets for "for" statements with tuple unpacking #6704

Patch from Frank Wierzbicki.
diff --git a/Misc/NEWS b/Misc/NEWS
index 5c467aa..04e28da 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
 Core and Builtins
 -----------------
 
+- Issue #6704: Improve the col_offset in AST for "for" statements with
+  a target of tuple unpacking.
+
 - Issue #6707: dir() on an uninitialized module caused a crash.
 
 - Issue #6540: Fixed crash for bytearray.translate() with invalid parameters.