This commit:
* Adds a new subproject, audio_core.
* Defines structures that exist in DSP shared memory.
* Hooks up various other parts of the emulator into audio core.

This sets the foundation for a later HLE DSP implementation.

Followup to #1102
Original author @mailwl

Add a case of `Log::Class::Count` to the switch statement that
dispatches on `Log::Class`.  The case simply calls the `UNREACHABLE`
macro.

Use the UNREACHABLE macro instead of `ASSERT(false, ...);`.

Add a case of `Log::Level::Count` to all switch statements that
dispatch on `Log::Level`.  The case simply asserts `false` and notes
the invalid log level.

Implements unrotated planar YUV 4:2:0 -> RGB24 conversions in Y2R.
Currently only the Y (luma) channel is used, so the results don't
contain color. This will be added in a later PR at some point.

This is enough to get all currently know Moflex videos to decode. (Some
don't display on-screen due to seemingly unrelated reasons.)

Thanks to @archshift for doing the initial implementation which I
cleaned up and then fixed the 8x8 block mode.

It provided a large increase in complexity of the logging system while
having a negligible performance impact: the usage patterns of the ring
buffer meant that each log contended with the logging thread, causing
it to effectively act as a synchronous extra buffering.

Also removed some broken code related to filtering of subclasses which
was broken since it was introduced. (Which means no one ever used that
feature anyway, since, 8 months later, no one ever complained.)

Logging: check for filter before sending to the queue, to skip all heavy formatting on the other thread.

This was RE'd from the errdisp applet.

Fixes an assertion upon executing citra in debug mode.

Involves making asserts use printf instead of the log functions (log functions are asynchronous and, as such, the log won't be printed in time)
As such, the log type argument was removed (printf obviously can't use it, and it's made obsolete by the file and line printing)

Also removed some GEKKO cruft.

Implemented the required calls to make it work.

CoreTiming: Added a new logging class Core_Timing.

Stubbed CreateMemoryBlock

Using Berkeley sockets, and Winsock2.2 on Windows.
So far ftpony creates the socket and accepts incoming connections

SOC_U: Renamed functions to maintain consistency

Also prevents possible scope errors / conflicts with the actual Berkeley socket functions

SOCU: Close all the opened sockets when cleaning up SOCU