testcrypt: include a dputs() function.

This allows me to compile testcrypt with -DDEBUG, even though it's not
linked against the usual collection of platform-specific modules that
normally provide dputs. I think the simplest possible dputs ('just
output to stderr') is actually better for testcrypt, because that
keeps it easy to compile for strange experimental platforms.

testcrypt.c

@@ -992,6 +992,11 @@ static void free_all_values(void)
     freetree234(values);
 }
 
+void dputs(const char *buf)
+{
+    fputs(buf, stderr);
+}
+
 int main(int argc, char **argv)
 {
     const char *infile = NULL, *outfile = NULL;