Bug 970895: Use I/O loop for polling memory-pressure events, r=dhylands

The code for polling sysfs for memory-pressure events currently
runs on a separate thread. This patch implements this functionality
for the I/O thread. This unifies the code base a bit and also safes
some resources.
Bug 960894 - 1/4: allow representing multiple clients in one RIL worker. r=bz
Bug 960894 - 2.a/4: move ril_worker init code out of RadioInterfaceLayer ctor. r=hsinyi
Bug 960894 - 2.b/4: allow sharing WorkerMessenger between RadioInterface instances. r=hsinyi
Bug 960894 - 3.a/4: Move PENDING_NETWORK_TYPE into RIL and rename to pendingNetworkType. r=hsinyi
Bug 960894 - 3.b/4: don't modify global. r=hsinyi
Bug 960894 - 3.c/4: construct global objects from constructors. r=hsinyi
Bug 960894 - 3.d/4: look up foreign objects through 'this.context'. r=hsinyi
Bug 960894 - 3.d.2/4: use 'this.context.clientId'. r=hsinyi
Bug 960894 - 3.d.3/4: use 'this.context.debug'. r=hsinyi
Bug 960894 - 3.e/4: multiple contexts in one RIL worker. r=hsinyi
Bug 960894 - 3.f/4: really merge all RIL worker instances into one. r=hsinyi
Bug 960894 - 4/4: fix existing ril_worker test cases. r=hsinyi,yoshi
Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/52f1921ada2f
Author: Carmen Jiménez <cjc@tid.es>
Desc: Merge pull request #16223 from mcjimenez/bug923455

Bug 923455 - SV: Predictive text configurable by SIM

========

https://hg.mozilla.org/integration/gaia-central/rev/693cc2ffa414
Author: Carmen Jimenez Cabezas <cjc@tid.es>
Desc: Bug 923455 - SV: Predictive text configurable by SIM
Bumping manifests a=b2g-bump
Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/5a164a6156b4
Author: gitmai <mri@tid.es>
Desc: Merge pull request #15974 from gitmai/bug-968110-CC-javascript-error-when-notification-open-CC

Bug 968110 -[costcontrol] Javascript error when open a notification when...
r=salva

========

https://hg.mozilla.org/integration/gaia-central/rev/e10859c9f475
Author: mai <mri@tid.es>
Desc: Bug 968110 -[costcontrol] Javascript error when open a notification when the application is closed
Bumping manifests a=b2g-bump
Merge mozilla-central to b2g-inbound
Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/7c807b9e73ea
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #16171 from bebef1987/ftu_wifi

Bug 970828 - test_ftu_skip_tour often failing to connect to WiFi

========

https://hg.mozilla.org/integration/gaia-central/rev/fe054f31d9a8
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 970828 - test_ftu_skip_tour often failing to connect to WiFi
Bumping manifests a=b2g-bump