Track down required changes in 2001/anonymous

In order to know what had to change exactly I tested this out (though
it's possible I forgot to initially document changes and so I did not
test everything) and I have documented it in the README.md. The required
changes:

- remove infinite recursion from main(): move the body of main() to
another function.

- add #include <sys/mman.h> for mmap().

Without either this did not work. I also changed (in case of
non-standardised constants) '3' in the call to mmap() to be
PROT_READ|PROT_WRITE but this appears to not be strictly required.

I added the script try.me.sh which has more commands than the previous
try section to show how it works and what changes etc.

Updated .gitignore as the above script creates some.

Make make all attempt to compile anonymous.ten.c: it's an important part
of the program though it can work on other 32-bit ELF binaries.

Update bugs.md explaining why this won't work with macOS.

2001/anonymous/.gitignore

@@ -1,2 +1,6 @@
 anonymous
 anonymous.ten
+ten.bak.od
+ten.bak.txt
+ten.od
+ten.txt