Implement basic `Rtl*` functions

[mborgerson]

Many (but not all) of these functions are quite simple libc style routines that can be easily implemented.

Including:

• [ ] RtlAnsiStringToUnicodeString
• [ ] RtlAppendStringToString
• [ ] RtlAppendUnicodeStringToString
• [ ] RtlAppendUnicodeToString
• [ ] RtlAssert
• [ ] RtlCharToInteger
• [ ] RtlCompareMemory
• [ ] RtlCompareMemoryUlong
• [ ] RtlCompareString
• [ ] RtlCompareUnicodeString
• [ ] RtlCopyString
• [ ] RtlCopyUnicodeString
• [ ] RtlCreateUnicodeString
• [ ] RtlDowncaseUnicodeChar
• [ ] RtlDowncaseUnicodeString
• [ ] RtlEqualString
• [ ] RtlEqualUnicodeString
• [ ] RtlExtendedIntegerMultiply
• [ ] RtlExtendedLargeIntegerDivide
• [ ] RtlExtendedMagicDivide
• [ ] RtlFillMemory
• [ ] RtlFillMemoryUlong
• [ ] RtlFreeAnsiString
• [ ] RtlFreeUnicodeString
• [ ] RtlInitAnsiString
• [ ] RtlInitUnicodeString
• [ ] RtlIntegerToChar
• [ ] RtlIntegerToUnicodeString
• [ ] RtlLowerChar
• [ ] RtlMoveMemory
• [ ] RtlMultiByteToUnicodeN
• [ ] RtlMultiByteToUnicodeSize
• [ ] RtlNtStatusToDosError
• [ ] RtlTimeFieldsToTime
• [ ] RtlTimeToTimeFields
• [ ] RtlUlongByteSwap
• [ ] RtlUnicodeStringToAnsiString
• [ ] RtlUnicodeStringToInteger
• [ ] RtlUnicodeToMultiByteN
• [ ] RtlUnicodeToMultiByteSize
• [ ] RtlUpcaseUnicodeChar
• [ ] RtlUpcaseUnicodeString
• [ ] RtlUpcaseUnicodeToMultiByteN
• [ ] RtlUpperChar
• [ ] RtlUpperString
• [ ] RtlUshortByteSwap
• [ ] RtlZeroMemory