Add alt supplementary program to 2001/anonymous

Running make alt will compile the anonymous.ten.c without specifying
-m32: whether it'll end up being 64-bit or not would depend on the
system but it'll be saved as anonymous.ten.64 anyway.

The try.me.sh script will run this program directly, skipping the entry
itself, if the anonymous.ten.c cannot be compiled as a 32-bit binary.

Updated .gitignore.

2001/anonymous/README.md

@@ -82,6 +82,8 @@ What happens if you try it on another file like [anonymous.c](anonymous.c)? Can
 you recompile it okay? What if you run it on `anonymous` itself? Can you run the
 program successfully after it without recompiling?
 
+NOTE: if the 32-bit version cannot be compiled the script will at least run the
+alternate version of the [anonymous.ten](anonymous.ten.c) program.
 
 ## Judges' remarks: