Convert SendInput primitives to blittable types

[X9VoiD]

Changes

• Use fixed byte array for manual blitting of union structures.
• Remove unneeded keyboard SendInput allocation.
• Perform zero-copy SendInput by allowing the primitives to be blittable and not require further marshalling by CLR.

Other changes

• Fix driver detection crash when running on 32-on-64 bit situations.
• Allow for 32 bit compatibility when OTDPLATFORM32 constant is defined.