GH540: add casts to safestack.h

Signed-off-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Dr. Stephen Henson <steve@openssl.org>

util/mkstack.pl

diff --git a/util/mkstack.pl b/util/mkstack.pl
index 06cf0f9..eae3d55 100755
--- a/util/mkstack.pl
+++ b/util/mkstack.pl
@@ -125,7 +125,7 @@
     } \
     static ossl_inline t2 *sk_##t1##_value(const STACK_OF(t1) *sk, int idx) \
     { \
-        return sk_value((_STACK *)sk, idx); \
+        return (t2 *)sk_value((_STACK *)sk, idx); \
     } \
     static ossl_inline STACK_OF(t1) *sk_##t1##_new(int (*cmpf)(const t3 * const *a, const t3 * const *b)) \
     { \
@@ -145,11 +145,11 @@
     } \
     static ossl_inline t2 *sk_##t1##_delete(STACK_OF(t1) *sk, int i) \
     { \
-        return sk_delete((_STACK *)sk, i); \
+        return (t2 *)sk_delete((_STACK *)sk, i); \
     } \
     static ossl_inline t2 *sk_##t1##_delete_ptr(STACK_OF(t1) *sk, t2 *ptr) \
     { \
-        return sk_delete_ptr((_STACK *)sk, (void *)ptr); \
+        return (t2 *)sk_delete_ptr((_STACK *)sk, (void *)ptr); \
     } \
     static ossl_inline int sk_##t1##_push(STACK_OF(t1) *sk, t2 *ptr) \
     { \
@@ -177,7 +177,7 @@
     } \
     static ossl_inline t2 *sk_##t1##_set(STACK_OF(t1) *sk, int idx, t2 *ptr) \
     { \
-        return sk_set((_STACK *)sk, idx, (void *)ptr); \
+        return (t2 *)sk_set((_STACK *)sk, idx, (void *)ptr); \
     } \
     static ossl_inline int sk_##t1##_find(STACK_OF(t1) *sk, t2 *ptr) \
     { \