Document the change.

CHANGES

@@ -3,6 +3,13 @@
 
  Changes between 0.9.6 and 0.9.7  [xx XXX 2000]
 
+  *) Make SMIME_write_PKCS7() write mail header values with a format that
+     is more generally accepted (no spaces before the semicolon), since
+     some programs can't parse those values properly otherwise.  Also make
+     sure BIO's that break lines after each write do not create invalid
+     headers.
+     [Richard Levitte]
+
   *) Make sk_sort() tolerate a NULL argument.
      [Steve Henson reported by Massimiliano Pala <madwolf@comune.modena.it>]