stupidgcm: fix openssl 1.1 build failure

Fixed by including the correct header. Should work on older openssl
versions as well.

Error was:
locking.go:21: undefined reference to `CRYPTO_set_locking_callback'

Author: rfjakob

internal/stupidgcm/locking.go

@@ -8,7 +8,7 @@ package stupidgcm
 // has been removed completely in openssl 1.1.0.
 
 /*
-#include <openssl/evp.h>
+#include <openssl/crypto.h>
 #include <stdio.h>
 
 static void dummy_callback(int mode, int n, const char *file, int line) {