Tests for exact power on timing

[alyosha-tas]

Here is test that checks the state of the clock divider the timers use after power on:

https://github.com/alyosha-tas/gba-tests/tree/master/timer

The resolution of this test is one clock cycle:

Test 3 reads the state of the timer exactly on rollover of the divider. Test 6 reads the state of the timer 1 cycle after it should have roller over. Test 9 reads the state of the timer 1 cycle before it should roll over.

Tested on GBP. Nanoboy Advance currently fails test 1.

[fleroviux]

Thanks for all the tests! I hope I can find some energy soon to finish my prefetch buffer rewrite and look at all the new tests.