Move utils filename list into its own subdir.

Now there's a utils/CMakeLists.txt, which contains the huge list of
source files in that directory, so that the top-level file does a
better job of showing the overview.

utils/CMakeLists.txt

@@ -0,0 +1,56 @@
+add_sources_from_current_dir(utils
+  base64_decode_atom.c
+  base64_encode_atom.c
+  bufchain.c
+  buildinfo.c
+  burnstr.c
+  chomp.c
+  conf.c
+  conf_dest.c
+  conf_launchable.c
+  ctrlparse.c
+  debug.c
+  dupcat.c
+  dupprintf.c
+  dupstr.c
+  encode_utf8.c
+  fgetline.c
+  host_strchr.c
+  host_strchr_internal.c
+  host_strcspn.c
+  host_strduptrim.c
+  host_strrchr.c
+  marshal.c
+  memory.c
+  memxor.c
+  miscucs.c
+  null_lp.c
+  nullseat.c
+  nullstrcmp.c
+  out_of_memory.c
+  parse_blocksize.c
+  prompts.c
+  ptrlen.c
+  read_file_into.c
+  seat_connection_fatal.c
+  sessprep.c
+  sk_free_peer_info.c
+  smemclr.c
+  smemeq.c
+  ssh2_pick_fingerprint.c
+  sshutils.c
+  strbuf.c
+  string_length_for_printf.c
+  stripctrl.c
+  tree234.c
+  validate_manual_hostkey.c
+  version.c
+  wcwidth.c
+  wildcard.c
+  write_c_string_literal.c
+  x11authfile.c
+  x11authnames.c
+  x11_dehexify.c
+  x11_identify_auth_proto.c
+  x11_make_greeting.c
+  x11_parse_ip.c)