enable coveralls support
Move simplify_filename from tag.c
Move functions from window.c
Move fix_fname from buffer.c
Move after_pathsep from misc2.c
Move same_directory from misc2.c
Move pathcmp from misc2.c
Move mch_expandpath from os_unix.c
Move shorten_fname{,1,s} and shorten_filenames from fileio.c
Move expand_wildcards{,_eval} from misc1.c
Move match_suffix from misc1.c
Move shorten_filenames back to fileio.c