Make methods of |RAND_SSLEay| do reasonable things.

This means e.g. that a caller can say:

  RAND_SSLEay()->bytes(...)

and so on.  But in exchange for this convenience, I've changed the
signatures to be more BoringSSL-ish (|size_t| instead of |int|).
That's fine; |RAND_set_rand_method(SSLEay())| still works.  And by
works I mean "does nothing".

Change-Id: I35479b5efb759da910ce46e22298168b78c9edcf
Reviewed-on: https://boringssl-review.googlesource.com/5472
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/rand.h b/include/openssl/rand.h
index 2918c7e..335c76e 100644
--- a/include/openssl/rand.h
+++ b/include/openssl/rand.h
@@ -76,10 +76,10 @@
  * external so that variables of this type can be initialized. */
 struct rand_meth_st {
   void (*seed) (const void *buf, int num);
-  int (*bytes) (unsigned char *buf, int num);
+  int (*bytes) (uint8_t *buf, size_t num);
   void (*cleanup) (void);
   void (*add) (const void *buf, int num, double entropy);
-  int (*pseudorand) (unsigned char *buf, int num);
+  int (*pseudorand) (uint8_t *buf, size_t num);
   int (*status) (void);
 };