Fix some clang warnings

Clang was complaining about some unused functions. Moving the stack
declaration to the header seems to sort it. Also the certstatus variable
in dtlstest needed to be declared static.

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

test/dtlstest.c

@@ -23,7 +23,7 @@ static char *privkey = NULL;
 
 #define DUMMY_CERT_STATUS_LEN  12
 
-unsigned char certstatus[] = {
+static unsigned char certstatus[] = {
     SSL3_RT_HANDSHAKE, /* Content type */
     0xfe, 0xfd, /* Record version */
     0, 1, /* Epoch */

test/ssltestlib.c

@@ -238,8 +238,6 @@ typedef struct mempacket_st {
     unsigned int type;
 } MEMPACKET;
 
-DEFINE_STACK_OF(MEMPACKET)
-
 static void mempacket_free(MEMPACKET *pkt)
 {
     if (pkt->data != NULL)

test/ssltestlib.h

@@ -33,4 +33,8 @@ void bio_s_mempacket_test_free(void);
 int mempacket_test_inject(BIO *bio, const char *in, int inl, int pktnum,
                           int type);
 
+typedef struct mempacket_st MEMPACKET;
+
+DEFINE_STACK_OF(MEMPACKET)
+
 #endif /* HEADER_SSLTESTLIB_H */