Document in CHANGES that config now recognises 64-bit mingw

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2917)
diff --git a/CHANGES b/CHANGES
index 12a9c92..b6d5332 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,10 @@
 
  Changes between 1.1.0e and 1.1.1 [xx XXX xxxx]
 
+  *) Have 'config' recognise 64-bit mingw and choose 'mingw64' as the target
+     platform rather than 'mingw'.
+     [Richard Levitte]
+
   *) x86_64 assembly pack: annotate code with DWARF CFI directives to
      facilitate stack unwinding even from assembly subroutines.
      [Andy Polyakov]