clarify which functions are the CMS functions which must have CMS_PARTIAL set

Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7960)

(cherry picked from commit 61e033308b1c004bd808352fb1d786547dcdf62b)

doc/man3/CMS_get0_type.pod

@@ -20,7 +20,8 @@ an ASN1_OBJECT pointer. An application can then decide how to process the
 CMS_ContentInfo structure based on this value.
 
 CMS_set1_eContentType() sets the embedded content type of a CMS_ContentInfo
-structure. It should be called with CMS functions with the B<CMS_PARTIAL>
+structure. It should be called with CMS functions (such as L<CMS_sign>, L<CMS_encrypt>)
+with the B<CMS_PARTIAL>
 flag and B<before> the structure is finalised, otherwise the results are
 undefined.