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

 /* Define to 1 if you have CPLEX. */

 #undef HAVE_CPLEX

 /* Define to 1 if you have GLPK. */

 #undef HAVE_GLPK