Better source unifier

- now it is called scripts/unify-sources.sh
- replaces each tab with 8 spaces
- remove trailing spaces (and tabs)
- warnings on long lines (i.e. on lines that are more than 80 characters)
- the standard file header now turns off the space-to-tab replacement in Emacs

 include_directories (${LEMON_SOURCE_DIR})

 add_library (lemon arg_parser.cc base.cc color.cc random.cc)