remove malloc casts

Following ANSI C rules, remove the casts from calls to
OPENSSL_malloc and OPENSSL_realloc.

Reviewed-by: Richard Levitte <levitte@openssl.org>
diff --git a/test/dhtest.c b/test/dhtest.c
index 6c063da..35bd298 100644
--- a/test/dhtest.c
+++ b/test/dhtest.c
@@ -165,7 +165,7 @@
     BIO_puts(out, "\n");
 
     alen = DH_size(a);
-    abuf = (unsigned char *)OPENSSL_malloc(alen);
+    abuf = OPENSSL_malloc(alen);
     aout = DH_compute_key(abuf, b->pub_key, a);
 
     BIO_puts(out, "key1 =");
@@ -176,7 +176,7 @@
     BIO_puts(out, "\n");
 
     blen = DH_size(b);
-    bbuf = (unsigned char *)OPENSSL_malloc(blen);
+    bbuf = OPENSSL_malloc(blen);
     bout = DH_compute_key(bbuf, a->pub_key, b);
 
     BIO_puts(out, "key2 =");