* Introduced ToxExt and CoreExt abstraction
* Along with interfaces for mocking and unit testing
* Add "supportedExtensions" concept to Friend
* Dispatch messages to CoreExt instead of Core when friend supports
extended messages
* Only split messages for core when extended messages are unavailable
* Offline message engine/History not altered. Currently only valid for
an existing session after extension negotiation has completed
* Reorder class data members and/or constructor initialisers to match,
reducing confusion about when members will be initialised.
* Remove (most) unused variables. Not removed: some global variables with
`TODO(sudden6)` on them for using them in the future. I don't know how
far into the future sudden6 wants to use them, so I left them there for
now.
* Distinguish different bootstrap nodes in the logs by index in the
bootstrap node list. Originally, we used to log the address/port of the
node we're bootstrapping to. This was removed out of privacy concerns
(even though the bootstrap nodes are public). This made the logs much
less useful when debugging why the client isn't connecting. Having
indices makes it easier to see that different nodes are being selected,
and makes it possible to determine which node was selected.
* Explicitly cast unused results of Tox API functions to `void` when all
we want is to know whether the function succeeds or not.
* Don't try to `#include <unistd.h>` on Windows. It does not exist on
MSVC.
* Remove extra `;` after function definitions.
* Remove reference indirection of QJsonValueRef, since a copy of that ref
(small pointer-like object) has to be made anyway when iterating over
QJsonArrays.
* Make some file-scope global state `static`.
* Use `nullptr` instead of `NULL`.
* Add `#if DESKTOP_NOTIFICATIONS` around the code that implements desktop
notifications, so it becomes a bit easier to compile everything with a
single compiler command - useful for manually running static analysers.
* Fix an error on MSVC where `disconnect` is looked up to be a non-static
member function and the `this` capture is missing.
* Consistently use `struct` and `class` tags for types.
* Use references in ranged-for where it reduces copies.
* Move private static data members out of the Style class and into
file-local scope. There is no need for them to be in the class. Also
marked them `const` where possible.
* Removed unused lambda capture.
* Ensure qTox can compile under NDEBUG with `-Wunused-variable` by
inlining the unused variable into the `assert` that was its only
target.
* Minor reformatting in core_test.cpp.
