Update a comment to match r875303 changes.

* subversion/include/svn_types.h: Update the overview comment about
  special files to use the new function name in libsvn_subr/subst.c.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1751399 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/subversion/include/svn_types.h b/subversion/include/svn_types.h
index f1a0850..710560f 100644
--- a/subversion/include/svn_types.h
+++ b/subversion/include/svn_types.h
@@ -416,7 +416,7 @@
  *  2. Creating a new textual name similar to
  *     SVN_SUBST__SPECIAL_LINK_STR in libsvn_subr/subst.c.
  *  3. Handling the translation/detranslation case for the new type in
- *     create_special_file and detranslate_special_file, using the
+ *     create_special_file_from_stream and detranslate_special_file, using the
  *     routines from 1.
  */