Updates and fixes to 2013/dlowe

Added fun.c and make make all compile it: this is what the judges
suggested one try compiling with different compilers and checking the
results. I added how to specify the compiler.

Added slen.sh script, corrected for shellcheck, which runs the command
the author suggested (and which the judges added to their remarks), to
make it simpler for viewers of the entry.

Added INABIAF section to README.md: if no args are specified it will
very likely crash or do something funny. A similar such thing is in
bugs.md as well.

Updated .gitignore.

Format fix README.md.

bugs.md

@@ -1840,6 +1840,19 @@ The file is `hd.img`.
 
 Do you have it? Please provide it!
 
+## [2013/dlowe](2013/dlowe/dlowe.c) ([README.md](2013/dlowe/README.md))
+## STATUS: INABIAF - please **DO NOT** fix
+
+This program will very likely crash or draw something strange with 0 args. Then
+again it might not. :-) This is easy to fix but would add bytes and since the
+author noted it is a feature and not a bug. You of course can try and fix it
+yourself but please do NOT open a pull request for this: just do it as an
+exercise to see if you understand the code.
+
+You can try and answer the questions, too: when will it crash? When will it draw
+something funny (or will it? :-) ) and when will it just do nothing?
+
+
 # 2014