If a program accidentally ends up linking in both libnm and libnm-util
(presumably via different dependencies), error out immediately.

Since libnm-util is no longer used from within NM, its copy of
NM_UTIL_PRIVATE_CALL is now useless, and the internal-only
NMSettingIP4Config:address-labels property is no longer needed.

Fix indentation, kill trailing whitespace, split some long lines.

- Remove list of authors from files that had them; these serve no
  purpose except to quickly get out of date (and were only used in
  libnm-util and not libnm-glib anyway).

- Just say "Copyright", not "(C) Copyright" or "Copyright (C)"

- Put copyright statement after the license, not before

- Remove "NetworkManager - Network link manager" from the few files
  that contained it, and "libnm_glib -- Access network status &
  information from glib applications" from the many files that
  contained it.

- Remove vim modeline from nm-device-olpc-mesh.[ch], add emacs modeline
  to files that were missing it.

g-i allows you to specify types in annotations using either their
fully-qualified introspected names (eg, "NMClient.Device") or their
plain C names ("NMDevice"). Switch from the former to the latter (so
that they'll still be correct when migrated to libnm later).

No reason to have two differently named files for the
same general purpose.

We made the UIs consistent last year, but missed the documentation.
Fix the docs to also consistently use "Wi-Fi" rather than "WiFi",
"Wifi", "wifi", or "WiFI"; "Ethernet" rather than "ethernet"; and
"InfiniBand" rather than "Infiniband".

The G_DISABLE_CHECKS version of g_return_if_reached() still returns,
it just doesn't log. So don't include a manual return after a
return-if-reached.