Core: Make CPU_POWERDOWN the initial CPU state.

This isn't a correct state for the CPU to begin in when starting the application.

Also CPU_STEPPING as an initial state causes the emulator to crash if you use any of the debugger stepping buttons, since it checks if the CPU is in the CPU_STEPPING state before performing their functions.
DolphinWX: Fix a possible crash when setting debugger memory values.
IOWin: Make error 0x1F less noisy.

This error code is used by third-party WiiMote adapters to signal the
absence of a WiiMote connected to their virtual HID port. Ignoring it
removes some log spamming and doesn't change anything in terms of
behavior.
IOWin: rework _IOWrite OVERLAPPED/bytes written handling.

CheckDeviceType_Write uses an OVERLAPPED structure to make sure some bytes
were written to the device for a given _IOWrite operation. However, the
OVERLAPPED structure is only used for the BlueSoleil stack, not the MS stack
(which goes through an alternate HID path instead of WriteFile, and does not
have an equivalent async operation).

Make _IOWrite return the number of written bytes instead, since it knows
about the Bluetooth stack being used.
Merge pull request #661 from delroth/dolphinbar

Fix WiiMote issues causing DolphinBar to not work
Merge pull request #655 from lioncash/crashes

Fix two possible crashes related to the debugger.