Add Mock OEMCrypto Stub

I added a Mock OEMCrypto implementation with stubs only.

I corrected the "extern C" location in OEMCrypto.h. (Thanks, Jerry!)

I added some Android.mk files that allows us to compile and
run a few simple unit tests.

Unit Test 1: The library compiles. (passes)
Unit Test 2: The test program links and runs. (passes)

Change-Id: Ib4c9554553de49645b5841b0bae889728cbfc8b1

libwvdrmengine/oemcrypto/include/OEMCrypto.h

@@ -6,8 +6,12 @@
  * Reference APIs needed to support Widevine's crypto algorithms.
  *********************************************************************/
 
-#ifndef _WIDEVINE_OEMCRYPTO_AES_H
-#define _WIDEVINE_OEMCRYPTO_AES_H
+#ifndef WV_OEMCRYPTO_H_
+#define WV_OEMCRYPTO_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 #define OEMCRYPTO_VERSION "4.0"
 static const char oec_version[] = OEMCRYPTO_VERSION;
@@ -93,10 +97,6 @@ typedef struct
     OEMCrypto_UINT32 key_control_offset;
 } OEMCrypto_KeyRefreshObject;
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #define OEMCrypto_Initialize _oec01
 #define OEMCrypto_Terminate _oec02
 #define OEMCrypto_SetEntitlementKey _oec03
@@ -643,7 +643,7 @@ OEMCryptoResult OEMCrypto_DecryptCTR(OEMCrypto_SESSION session_id,
                                      OEMCrypto_UINT32 key_id_length,
                                      const OEMCrypto_UINT8 *iv,
                                      OEMCrypto_UINT32 offset,
-                                     OEMCrypto_UINT32 data_length)
+                                     OEMCrypto_UINT32 data_length);
 
 /*
  * OEMCrypto_InstallKeybox
@@ -815,4 +815,4 @@ OEMCryptoResult OEMCrypto_DecryptCTS(OEMCrypto_UINT8 *pSrcBuf,
 }
 #endif
 
-#endif  // _WIDEVINE_OEMCRYPTO_AES_H
+#endif  // WV_OEMCRYPTO_H_