OEMCrypto v11 Documentation and Headers

Merge from widevine repo of http://go/wvgerrit/16186

These are the OEMCrypto v11 documents and header files. I have updated
just enough code so that existing unit tests pass.  New unit tests,
the reference implementation, and the level 3 implementation are in
future CLs.

Change-Id: I9bbf1909e047f63a5877320a2d06740a3c4a3e32

libwvdrmengine/cdm/core/src/crypto_session.cpp

@@ -683,10 +683,11 @@ CdmResponseType CryptoSession::Decrypt(const CdmDecryptionParameters& params) {
         }
       }
     }
-    sts = OEMCrypto_DecryptCTR(
+    // TODO(rfrias): add encrypt pattern parameter.
+    sts = OEMCrypto_DecryptCENC(
         oec_session_id_, params.encrypt_buffer, params.encrypt_length,
         params.is_encrypted, &(*params.iv).front(), params.block_offset,
-        &buffer_descriptor, params.subsample_flags);
+        &buffer_descriptor, NULL, params.subsample_flags);
   }
 
   switch (sts) {