- use _NM_GET_PRIVATE() and _NM_GET_PRIVATE_PTR() everywhere.

- reorder statements, to have GObject related functions (init, dispose,
  constructed) at the bottom of each file and in a consistent order w.r.t.
  each other.

- unify whitespaces in signal and properties declarations.

- use NM_GOBJECT_PROPERTIES_DEFINE() and _notify()

- drop unused signal slots in class structures

- drop unused header files for device factories

(cherry picked from commit 640fbec855907b19952c8f0411f8500f1008fd7d)

- don't include "nm-default.h" in header files. Every source file must
  include as first header "nm-default.h", thus our headers get the
  default include already implicitly.

- we don't support compiling NetworkManager itself with a C++ compiler. Remove
  G_BEGIN_DECLS/G_END_DECLS from internal headers. We do however support
  users of libnm to use C++, thus they stay in public headers.

(cherry picked from commit f19aff89095ca192b8b2e37534b7a899aecd82f9)

Fixes: b9f00dbb19de9120658c001d3e97cba67c5060f2

WiMAX support was dropped in commit 721e917cb6c3f6bea7e856aaed0cd49626887db1.
Also, remove support for the WiMAX rfkill flag and only preserve the
D-Bus property for backward compatibility.

Rather than randomly including one or more of <glib.h>,
<glib-object.h>, and <gio/gio.h> everywhere (and forgetting to include
"nm-glib-compat.h" most of the time), rename nm-glib-compat.h to
nm-glib.h, include <gio/gio.h> from there, and then change all .c
files in NM to include "nm-glib.h" rather than including the glib
headers directly.

(Public headers files still have to include the real glib headers,
since nm-glib.h isn't installed...)

Also, remove glib includes from header files that are already
including a base object header file (which must itself already include
the glib headers).

Previously, src/nm-ip4-config.h, libnm/nm-ip4-config.h, and
libnm-glib/nm-ip4-config.h all used "NM_IP4_CONFIG_H" as an include
guard, which meant that nm-test-utils.h could not tell which of them
was being included (and so, eg, if you tried to include
nm-ip4-config.h in a libnm test, it would fail to compile because
nm-test-utils.h was referring to symbols in src/nm-ip4-config.h).

Fix this by changing the include guards in the non-API-stable parts of
the tree:

  - libnm-glib/nm-ip4-config.h remains   NM_IP4_CONFIG_H
  - libnm/nm-ip4-config.h now uses     __NM_IP4_CONFIG_H__
  - src/nm-ip4-config.h now uses       __NETWORKMANAGER_IP4_CONFIG_H__

And likewise for all other headers.

The two non-"nm"-prefixed headers, libnm/NetworkManager.h and
src/NetworkManagerUtils.h are now __NETWORKMANAGER_H__ and
__NETWORKMANAGER_UTILS_H__ respectively, which, while not entirely
consistent with the general scheme, do still mostly make sense in
isolation.

Clean up some of the cross-includes between headers (which made it so
that, eg, if you included NetworkManagerUtils.h in a test program, you
would need to build the test with -I$(top_srcdir)/src/platform, and if
you included nm-device.h you'd need $(POLKIT_CFLAGS)) by moving all
GObject struct definitions for src/ and src/settings/ into nm-types.h
(which already existed to solve the NMDevice/NMActRequest circular
references).

Update various .c files to explicitly include the headers they used to
get implicitly, and remove some now-unnecessary -I options from
Makefiles.