RTC revamp (#1867)

* get this started

* implement DSi RTC commands

* set up RTC clock timer. lay down basic idea of a clock.

* make the date/time registers writable

* move RTC state to its own structure, to make it easier to deal with

* more RTC work
lay base for date/time dialog

* get the bulk of the RTC functionality going

* much simpler design for RTC stuff

* aha, that is what it is

* start working on the RTC IRQ

* implement all types of RTC IRQ

* start refining sleep mode. code still kinda sucks.

* implement keypad IRQ

* refine it some more

* shut the fuck uuuuuupppppppppppppp

src/SPI_Firmware.h

@@ -396,7 +396,7 @@ union UserData
         u8 TouchCalibrationPixel2[2];
         u16 Settings;
         u8 Year;
-        u8 Unknown1;
+        u8 RTCClockAdjust;
         u32 RTCOffset;
         u8 Unused2[4];
         u16 UpdateCounter;