Make 1991/dds C generated code use fgets()

This took less time than the previous fix (to let it work with clang)
because after stupidly doing the decryption/encryption manually I had
decided to write a simple program that does it instead.

Now systems won't whine about gets() being unsafe.

The thanks file further documents how this was done and the bugs.md file
no longer has this entry.

bugs.md

@@ -604,18 +604,6 @@ where this occurred was fixed but this one should not be fixed. Thank you.
 
 ## 1991 dds
 
-### STATUS: uses gets() - change to fgets() if possible
-### Source code: [1991/dds/dds.c](1991/dds/dds.c)
-### Information: [1991/dds/README.md](1991/dds/README.md)
-
-The compiled code uses `gets()` not `fgets()`. Can you fix this?  It's quite
-complicated to do: the `s` array is certainly relevant and you can see a bit of
-the magic in the [thanks](/thanks-for-fixes.md) and the README.md file for how
-it works. It's easy enough to get the code to refer to `fgets()` and call it
-correctly but it might take more work to get the generated code sorted. This
-will be looked at later.
-
-
 ## 1991 westley
 
 ### STATUS: INABIAF - please **DO NOT** fix