wwan: split out WWAN IP4Config from device config

We want to set the WWAN config last, to ensure that the configuration we
use overwrites anything that pppd might have set, becuase it touches some
stuff itself.  That means we have to keep the WWAN config separate, since
dev_ip4_config is used for DHCP and IPv4LL, which we always set first to
ensure they these don't overwrite external, administrator added config
(eg, priv->ext_ip4_config).

This also synchronizes the IPv4 config path with the upcoming IPv6
config path.
ppp: add IPv6 support

Add support for IPv6 to the pppd plugin and return the interface identifiers
to NetworkManager.  Use those to construct the IPv6LL addresses for the
PPP interface and the peer.
wwan: read supported IP types from ModemManager

Not all modems support IPv6, and to prevent some common failure
cases, make sure we don't try to use IPv6 when the modem doesn't
support it.
wwan: clean up and split IP method values

Add an 'unknown' value; make the type an enum, and rename it since
this enum is private to NetworkManager and abstracts differences
in old and new MM.

We also need separate methods for IPv4 and IPv6 since they may not
use the same mechanism.  For example, IPv4 may use DHCP but IPv6 may
require static configuration, based on what the modem firmware wants.
wwan: add infrastructure for IPv6 config results
wwan: add IPv6 support for ModemManager1 (bgo #682623)

https://bugzilla.gnome.org/show_bug.cgi?id=682623
wwan: move IP method handling into the modem object

Do it in one place (NMModem) so that NMDeviceBt takes advantage of
the same logic that NMDeviceModem used to use.
core: remove child devices when a parent's ip_iface becomes known

Child devices shouldn't be exposed as real NMDevices (yet) since the
configuration and life cycle is controlled by the parent.  We already
do this if the ip_iface is known when the child device is added, but
PPP and other transient interfaces often show up just before we know
the parent's ip_iface.
wwan: don't disconnect if nothing to disconnect

Avoid this error:

NetworkManager[25181]: <warn> (cdc-wdm1): Failed to connect 'T-Mobile Internet': Connection requested IPv4 but IPv4 is unsuported by the modem.
NetworkManager[25181]: <info> (cdc-wdm1): device state change: prepare -> failed (reason 'modem-init-failed') [40 120 28]

** (NetworkManager:25181): CRITICAL **: mm_modem_simple_disconnect: assertion 'MM_IS_MODEM_SIMPLE (self)' failed

self->priv->simple_iface is only valid if stage1/prepare actually
completes, so don't try to access it if stage1/prepare failed.
dhcp: DHCPv6 OtherConf failures should not be fatal

OtherConf implies the address has already been delivered via RA,
and possibly DNS too, meaning our IP configuration is already
good enough.  If nothing on the network bothers to reply to our
DHCPv6 Information Requests, let's just run with the config
we already have instead of tearing down the whole device.
wwan: use a shorter DHCP timeout

With WWAN, the DHCP is all done in modem firmware, and never started
until we know we have a successful packet connection to the network.
Which means the modem firmware already knows the IP details and
is ready to provide them.  Furthermore, since the DHCP is done on
what is essentially a reliable, wired point-to-point link, we don't
have to waste time with retransmits for dropped packets either.
merge: add WWAN support for IPv6 (bgo #682623)
wwan: allow completing new GSM connections without an APN (bgo #729665)

In commit 215306f5 [1], NetworkManager was changed to require an APN for GSM
connections; previously, an omitted APN was taken as "use the default APN
for this device".

ModemManager supports this behaviour with an empty APN string; older
NetworkManager versions support this behaviour with no APN in the
settings. Choose the older NM behaviour, for backwards compatibility.

[1] commit 215306f5a1e4dc38ec02a484c31470bb048d668b
  Author: Dan Williams <dcbw@redhat.com>
  Date:   Mon Jan 10 23:39:12 2011 -0600

    core: add AddAndActivate D-Bus method

    Given connection details, complete the connection as well as possible
    using the given specific object and device, add it to system
    settings, and activate it all in one method.

Signed-off-by: Simon Farnsworth <simon.farnsworth@onelan.co.uk>

https://bugzilla.gnome.org/show_bug.cgi?id=729665
wwan: allow using the default subscription APN (bgo #729665)

If no APN is specified, passing "" to ModemManager indicates that
the connection should use the default subscription APN, which the
modem and the network determine themselves.  This doesn't work
with all modems and operators, but in that case the user can
specify the APN.
libnm-util: fix gtk-doc syntax in nm-version.h to avoid a warning
libnm-util: fix enum member names in a gtk-doc comment
ifcfg-rh: fix a crash on setting hostname with SELinux disabled (rh #1122826)

When SELinux is disabled, getfscreatecon() fails leaving se_ctx_prev undefined
and then later freecon (se_ctx_prev) fails with a crash. Initializing
se_ctx_prev to NULL fixes the crash. (It is fine to pass NULL context to
setfscreatecon()).

Testcase:
1) Enable ifcfg-rh plugin in /etc/NetworkManger/NetworkManger.conf
   plugins=ifcfg-rh
2) Edit /etc/sysconfig/selinux to contain
   SELINUX=disabled
3) Reboot
4) Set hostname via nmcli, nmtui or D-Bus SaveHostname() call
5) NM crashes

https://bugzilla.redhat.com/show_bug.cgi?id=1122826
libnm-glib: document some properties

Some libnm-glib object properties were only documented in the
GParamSpec strings, not via gtk-doc comments, so they became
undocumented when the paramspec strings went away. Fix that.

(Also fix incorrect gtk-doc syntax with several NMClient properties.)
libnm-glib: fix gtk-doc for NMClient:active-connections

Since previous commit dafe51e8819c31ef6c0a7e901e43e821e229650f,
the gtk-doc is no longer ignored. However, the angle brackets
add invalid XML characters to ./docs/libnm-glib/xml/nm-client.xml
This breaks the build.

    make[3]: Entering directory `./NetworkManager/docs/libnm-glib'
      DOC   Scanning header files
      DOC   Introspecting gobjects
      DOC   Building HTML
    ../xml/nm-client.xml:1110: parser error : Opening and ending tag mismatch: NMActiveConnection line 1109 and para
    </para></refsect2>
           ^
    ../xml/nm-client.xml:1110: parser error : Opening and ending tag mismatch: para line 1107 and refsect2
    </para></refsect2>
                      ^
    ../xml/nm-client.xml:1211: parser error : Opening and ending tag mismatch: refsect2 line 1104 and refsect1
    </refsect1>
               ^
    ../xml/nm-client.xml:1262: parser error : Opening and ending tag mismatch: refsect1 line 1095 and refentry
    </refentry>
               ^
    ../xml/nm-client.xml:1263: parser error : Premature end of data in tag refentry line 7

    ^
    ../libnm-glib-docs.xml:67: element include: XInclude error : could not load ../xml/nm-client.xml, and no fallback was found
    make[3]: *** [html-build.stamp] Error 6

Signed-off-by: Thomas Haller <thaller@redhat.com>
config: fix prototype of nm_config_get_connectivity_interval()

gcc warns:

    make[4]: Entering directory `/data/src/NetworkManager/src'
      CC       nm-device.lo
    In file included from devices/nm-device.c:73:0:
    ../src/config/nm-config.h:61:13: warning: type qualifiers ignored on function return type [-Wignored-qualifiers]
     const guint nm_config_get_connectivity_interval (NMConfig *config);
                 ^

Signed-off-by: Thomas Haller <thaller@redhat.com>