memset, memcpy, sizeof consistency fixes

Just as with the OPENSSL_malloc calls, consistently use sizeof(*ptr)
for memset and memcpy.  Remove needless casts for those functions.
For memset, replace alternative forms of zero with 0.

Reviewed-by: Richard Levitte <levitte@openssl.org>

crypto/pqueue/pqueue.c

@@ -91,7 +91,7 @@ pqueue_s *pqueue_new()
     if (pq == NULL)
         return NULL;
 
-    memset(pq, 0x00, sizeof(pqueue_s));
+    memset(pq, 0, sizeof(*pq));
     return pq;
 }