Added more list utility functions to support hydra.
Began rewriting hydra to use linked lists instead of vectors.
Finished rewrite of hydra not to use vectors.
Added append_intval to list module, for convenience.
Converted makefile to compile hydra as C, and fixed some typos.
Fixed minor errors in LL implementation.
Fixed bugs in hydra.c and the Makefile relating to POSIX compliance and freeing of entries returned by readdir().
Merge branch 'cpp-to-c'