Add a get_random_bytes() syscall to replace the SRPC-based implementation

src/shared/platform/nacl_global_secure_random.h

 /*
  * Copyright (c) 2011 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /*
  * NaCl Service Runtime.  Secure RNG.  Global singleton.
  */
 
 #ifndef NATIVE_CLIENT_SRC_TRUSTED_PLATFORM_NACL_GLOBAL_SECURE_RANDOM_H_
 #define NATIVE_CLIENT_SRC_TRUSTED_PLATFORM_NACL_GLOBAL_SECURE_RANDOM_H_
 
 #include "native_client/src/shared/platform/nacl_secure_random.h"
 #include "native_client/src/shared/platform/nacl_sync.h"
 
 void NaClGlobalSecureRngInit(void);
 
 void NaClGlobalSecureRngSwitchRngForTesting(struct NaClSecureRng *);
 
 void NaClGlobalSecureRngFini(void);
 
 int32_t NaClGlobalSecureRngUniform(int32_t range_max);
 
 uint32_t NaClGlobalSecureRngUint32(void);
 
+void NaClGlobalSecureRngGenerateBytes(uint8_t *buf, size_t buf_size);
+
 /*
  * Generate a random alpha-numeric name for a socket, a semaphore or some
  * other device.
  */
 void NaClGenerateRandomPath(char *path, int length);
 
 #endif  /* NATIVE_CLIENT_SRC_TRUSTED_PLATFORM_NACL_GLOBAL_SECURE_RANDOM_H_ */