Add emulation support of ANDed clock signal for Timer A

[sp1187]

Timer A in SPG2xx generates its clock signal by ANDing its two clock sources together which can be used for more complex timer patterns, but currently veesem only supports the trivial cases of one source generating a frequency and the other always being high or low.

While the more complex signals are not used often in commercial games, it might be useful for homebrew.

[SatellaGuyAlt]

You know, this may seem like a crackhead theory, but this has a incredibly small chance of being the cause of the problem in A Day In The Life of A Sponge.

[sp1187]

The emulator core currently stops the emulation with an error whenever the timer is configured to this state, so the emulator should have crashed if that was the case.

veesem/src/core/spg200/timer.cc

Line 199 in a569600

die("Unsupported timer A settings");