This one is the best filter generator
http://www-users.cs.york.ac.uk/~fisher/mkfilter/trad.html
Unfortunately, it started to fail at the C code generation. But, it emits has enough information in the form close to the C code so that you can reproduce the program similar to what Mike proposes. You do not need any extra libraries for that. Libraries may be useful when you want to update your coefficients (variable cutoff frequencies). I do not know algorithms to compute those coefficients in your program.
