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/include/oemcrypto_adapter.h

@@ -34,6 +34,7 @@ OEMCryptoResult OEMCrypto_GetNumberOfOpenSessions(SecurityLevel level,
                                                   size_t* count);
 OEMCryptoResult OEMCrypto_GetMaxNumberOfSessions(SecurityLevel level,
                                                  size_t* maximum);
+uint8_t OEMCrypto_Security_Patch_Level(SecurityLevel level);
 }  // namespace wvcdm
 
 #endif  // WVCDM_CORE_OEMCRYPTO_ADAPTER_H_