Further tweaking the alloca handling in Hashicorp plugin

plugin/hashicorp_key_management/hashicorp_key_management_plugin.cc

@@ -13,21 +13,17 @@
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */
 
+#include <my_global.h>
 #include <mysql/plugin_encryption.h>
 #include <mysqld_error.h>
 #include <string.h>
-#include <stdlib.h>
-#include <limits.h>
-#include <time.h>
 #include <errno.h>
 #include <string>
 #include <sstream>
 #include <curl/curl.h>
 #ifdef _WIN32
 #include <malloc.h>
 #define alloca _alloca
-#elif !defined(__FreeBSD__) && !defined(__NetBSD__) && !defined(__OpenBSD__) && !defined(__DragonFly__)
-#include <alloca.h>
 #endif
 #include <algorithm>
 #include <unordered_map>