enum classes are still considered complete types when forward declared
(as the compiler knows the exact size of the type from the declaration
alone). The only difference in this case being that the members of the
enum class aren't visible. Given we don't use the members within this
header in any way, we can simply forward declare them here and remove
the inclusions.
* The MSB for each byte in cpsr_ge were not being appropriately set.
* We also expand test coverage to test this case.
* We fix the disassembly of the MSR (imm) and MSR (reg) instructions as well.
