ppc: Model configurable CPU frequencies

[mihaip]

Virtual time previously advanced by a fixed 16 ns per interpreted instruction, making every CPU behave like the legacy 62.5 MHz model regardless of the selected machine. G3 guests also received ad hoc HID1 values from individual machine implementations, while Gazelle supported several frequencies that could not share that logic.

Require each machine to provide its hardware-appropriate bus, core, and timebase clocks through one PPC_CPU_Config configuration object. We can then derive things from it (e.g. supported MPC603ev and MPC750 HID1 PLL encodings). We can also populate the include_601 global based on version instead of a separate flag.

To model time with more flexibility, we now use 60.4 fixed-point nanoseconds for instruction timing. This lets us have a broad set of frequencies and still support running the CPU for ~35 years of virtual time before it overflows.

This results in two emulation accuracy improvements:

• Tiger successfully gets to the Finder. The virtual time we were exposing to the guest was advancing too quickly, preventing loginwindow from connecting before WindowServer's internal five-second no-client timer expired. The server then exited normally, loginwindow aborted when it could not establish its CoreGraphics connection, and we remained stuck at the last textual output from a verbose boot ("Waiting for IFC").
• Animations are now more accurate (e.g. Mac OS X dock icon bouncing is no longer too fast on a G3)

[dingusdev]

This is a very nice commit which cleans up the virtual timer. A small bonus is the nicer CPU initialization.

[mihaip]

(was reverted due to x86-64 performance issues, will try again)