setup src tree, clean out bin directory

The src tree now contains source for tools that will be published
as part of the IOCCC winner web site.  However, the compiled and/or
installed tools that install under bin, will NOT be published.
The bin directory is now excluded under .gitignore so that
those who use this repo will have to do:

```sh
cd src; make clobber all install
```

The src/Makefile in turn drives rules in sub-directory
Makefiles.  Currently there are only two sub-directories:

winner_name - a completely re-written extract_winner_handles.sh
sgit - run sed on all files under git control

The check_awards.sh tool was moved under tmp
as this tool depends on CSV file, will not be needed soon,
and will go away when the tmp directory is cleaned
out towards the end of finishing issue #4.

.gitignore

@@ -36,6 +36,7 @@
 /archive/2019/
 /archive/2020/
 /bugs.html
+/bin
 /faq.html
 iocccsize
 mkentry