Add tests for STMDB/STMIB with empty Rlist

[jsmolka]

Add tests for STMDB/STMIB with empty Rlist

[jsmolka]

@Ankeraout I think these tests already cover empty rlists in block transfer.

[Ankeraout]

They cover STMIA and LDMIA but not STMDB and STMIB.
We've discovered that at least 2 emulators (NanoboyAdvance and AmazinglyAdvanced) failed these 2 tests, while passing gba-suite's ARM test.

[jsmolka]

My emulator fails them aswell. I'll take a look at it during the weekend and add them to the test suite.

[jsmolka]

@Ankeraout I fixed the issue and added an additional test. Here is a short summary:

• stmda stores the pc at [rn - 0x3C]
• stmdb stores the pc at [rn - 0x40]
• stmia stores the pc at [rn + 0x00]
• stmib stores the pc at [rn + 0x04]

I'll take a look at the loads with empty rlist now and see if I missed something there.