Merge from Widevine repo of http://go/wvgerrit/27462
This updates the documentation for OEMCrypto:
1) Clarification on values for the key control block verification
field. Unit tests for this change are already in the code.
2) Clarification on how Offline License Release messages are signed.
And for the Android supplement:
3) liboemcrypto.so may be installed in several places.
b/38422219
Testing: docs only change. no testing needed.
Change-Id: Iab3f5b585a41c80c5d7aa5f00aabce2de2df3a79
32348b987c