Updates to OEMCrytpo Mock

Squash merge from the widevine repo of several changes to oemcrypto
unit tests and the mock reference code.

http://go/wvgerrit/16264 Use unsigned int for count in usage table (more mock)
http://go/wvgerrit/16262 Use unsigned int for count in usage table (mock version)
http://go/wvgerrit/16247 Fix mock OEMCrypto_DeleteUsageTable
http://go/wvgerrit/16070 Fix OEMCrypto_GenerateRSASignature return values
http://go/wvgerrit/15991 Fix buffer overflow for 32-bit systems
http://go/wvgerrit/15993 Return Correct Value from OEMCrypto_RefreshKeys
http://go/wvgerrit/15880 Cast RSA_size() to int
http://go/wvgerrit/15831 Be strict about warnings for CE CDM

b/23729420
b/25221168

Change-Id: I97b91dfc672db8c586ae317977871b7d6afac4bb

libwvdrmengine/oemcrypto/mock/src/oemcrypto_usage_table_mock.h

@@ -39,7 +39,7 @@ struct StoredUsageTable {
   uint8_t signature[SHA256_DIGEST_LENGTH];
   uint8_t iv[wvcdm::KEY_IV_SIZE];
   int64_t generation;
-  size_t count;
+  uint64_t count;
   AlignedStoredUsageEntry entries[];
 };