StdLibInteractiveIO

This is a fixed-up version of edk2's StdLib/LibC/Uefi/InteractiveIO, the line discipline porition of StdLib.

NOTE: StdExtLib, StdLibDevConsole, StdLibInteractiveIO and StdLibUefi all go together.

Differences:

• Honor c_cc[VEOF] as WEOF, breaking out of input on ^D.
• Do not treat errors (inside IIO_GetInChar) as WEOF.
• Properly percolate IIO_GetInChar errors through IIO_CanonRead.
• Properly percolate IIO_CanonRead/IIO_NonCanonRead return values through IIO_Read, making errors and 0 (e.g. VEOF) work correctly.
• Default VQUIT and VINTR to abort ongoing I/O with EIO.
• No default Termios initialization.
• Fix IIO_Echo calling fo_write with 0 bytes.
• Fix IIO_Write callling fo_write with 0 bytes (not seen in the wild, but...)
• Fix IIO_Write incorrectly treating CharLen as signed size, leading to crashes and unpredictable behavior on writes of binary data through IIO.
• Fix IIO_Write to allow printing wide NULs.
• Drop UTF8 support entirely. "POSIX" side is taken to be single-byte only. This may seem like loss of functionality, but in practice it will make, when combined with special "narrow" stdin/stdout variants and redirection, the UNIX tools work as expected on binary data (without corrupting it).

It seem InteractiveIO is its own ad-hoc, and very buggy implementation of a line discipline. That seems like a mistake. Many issues exist because I/O is done through the UEFI Shell and that expects UTF16-coded data (the weird Shell 'narrow' |a <a and >a are just broken as they expect printable NUL-terminated UTF16).