Fix pointer size issues with argv on VMS

The argument 'argv' in 'main' is a short pointer to a short pointer on
VMS, regardless of initial pointer size.  We must therefore make sure
that 'copy_argv' gets a 32-bit pointer for argv, and that the copied
argv is used for the rest of main().

This introduces the local type argv_t, which will have correct pointer
size in all cases (and be harmless on all other platforms) as well as
the macro Argv, which is defined as 'copied_argv' or 'argv', as the
case may be.

Reviewed-by: Andy Polyakov <appro@openssl.org>

apps/vms_decc_init.c

@@ -105,7 +105,8 @@ decc_feat_t decc_feat_array[] = {
     {(char *)NULL, 0}
 };
 
-char **copy_argv(int *argc, char *argv[])
+
+char **copy_argv(int *argc, argv_t argv)
 {
     /*-
      * The note below is for historical purpose.  On VMS now we always