Adding new source file

1. Add file(s).
2. Add it to src/Makefile.am and regenerate src/Makefile.in file.
3. Add it to src/Makefile.win.
4. Add its description to the README file (don't forget to update last modification time at the top).
5. When commiting do not forget to commit new files, e.g. use git add --intent path/to/file on each of them beforehand.