Fixed crash when sending then saving inline image.
Attempted fix of transfer of large files from 32bit machines.
Added munreks bootstrap node.
Safer saving, write to tox_save.tmp then rename it to tox_save.
Abstract i18n some more
Extract i18n initialization into ui_i18n.c

This allows be more explicit about language fallback
route, and change it per-language.

Localized strings are now accessed via a function call,
instead of exposing a big string array.

This allows additional bounds check with a visible canary
value, and further abstracts i18n implementation.
Italian translation: update
Add unused.h with UNUSED macro
Fix unused parameter warnings in obviously correct places
Fix unused parameter warnings for userdata in callbacks
Fix unused parameter warnings for Tox*.

We have a single global instance of Tox,
so in many places we don't care.
Mark unused coord/element parameters in UI functions.
Fix unused parameter warning in messages_set_typing()

is_typing state is directly extracted from friend/group,
that corresponds to the MESSAGES ui element.
Fix unused parameter warning for tox_thread()

Not used anywhere, and thread creators actually
just pass NULL there.
Merge pull request #433 from albel727/better-i18n-take-two

Better i18n take two
Merge pull request #436 from Ansa89/italian-translation

Italian translation: update
Rewrite context menus with i18n support

CONTEXTMENU struct is generalized by introducing
ondisplay() callback for fetching menu item strings,
and adding a userdata field.

One out-of-the-box CONTEXT variety is provided.

It treats userdata as an array of UI_STRING_IDs
to be displayed (beware, contextmenu_new() function
doesn't copy the array, so make sure it has proper lifespan).

All previously existed context menus are replaced with it.
Add i18n text for various dropdowns
Add russian-localized text for dropdown menus
Move hardcoded dropdown menus from .h to .c