Merge branch 'topic/shoens-2000'

Merge branch 'topic/shoens-2000'

* topic/shoens-2000:
  n_lex_input(): truly support line continuation via backslash..
  MLE: enable recursive command invocations
  (BWDIC!) Allow `source' in `call'ed macros..
  (TMP) collect.c: use sigman
  (TMP) send.c: use sigman where easily applicable
  Add n_str_assign() series, use my usual buffer style
  Move UI related string code to new ui_str.c
  Move argcount() to list.c
  Move message related code to new message.c
  Move shell word expansion plus code to new shexp.c
  Move socket code to new socket.c
  Move dotlock code to new dotlock.c
  Move path related code to new path.c
  Move string dope from strings.c to the new memory.c..
  Split memory handling off auxlily.c, to new memory.c
  Move mailbox/folder handling to new folder.c
  Add n_pager_{open,close}() -- _always_ termios(4) for $PAGER!
  cmd1.c: use sigman, needed for new colour..
  Outsource signal stuff to new signal.c..
  mk-conf.sh: this BSD software actually REQUIRES SA_RESTART!