Pipe 2 is a DSP pipe that is used to initialize both the DSP hardware (the
application signals to the DSP to initialize) and the application (the DSP
provides the memory location of structures in the shared memory region).

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.

This commit fixes several kernel object leaks. The most severe of them
was threads not being removed from the private handle table used for
CoreTiming events. This resulted in Threads never being released, which
in turn held references to Process, causing CodeSets to never be freed
when loading other applications.

along with more info being logged.

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.

They're finally unnecessary, and will stop cluttering the application's
handle table.

- Hack to work around games checking that the DSP event has been signaled by a real DSP interrupt.

This is a first step at fixing the conceptual insanity that is our
handling of service and IPC calls. For now, interfaces still directly
derived from Session because we don't have the infrastructure to do it
properly. (That is, Processes and scheduling them.)

Should theoretically push retail stuff further along

in the service's headers