Reimplement inline functions in ERC with define-inline.

Reimplement inline functions in ERC with define-inline.

* lisp/erc/erc-backend.el: (erc-server-reconnect-p): Reimplement using
  define-inline.

* lisp/erc/erc-dcc.el: (erc-dcc-unquote-filename, erc-dcc-get-parent):
  Reimplement using define-inline.

* lisp/erc/erc-services.el: (erc-nickserv-alist-sender,
  erc-nickserv-alist-regexp, erc-nickserv-alist-nickserv,
  erc-nickserv-alist-ident-keyword, erc-nickserv-alist-use-nick-p,
  erc-nickserv-alist-ident-command,
  erc-nickserv-alist-identified-regexp): Reimplement using define-inline.

* lisp/erc/erc.el: (erc-get-channel-user, erc-get-server-user,
  erc-add-server-user, erc-remove-server-user, erc-channel-user-owner-p,
  erc-channel-user-admin-p, erc-channel-user-op-p,
  erc-channel-user-halfop-p, erc-channel-user-voice-p, erc-log):
  Reimplement using define-inline.