[Feature] Parsing of binary streams instead of utf-8?

ANTLR should support the parsing of raw binary streams (1 byte per input character) alongside UTF-8 characters.

have it available as an encoding, for example:
`antlr4 -encoding raw Grammar.g4`

For example to match the byte `0x80` it is not possible right now as `\u0080` evaluates to `0xC280`

Start by reviewing ANTLR's input-stream handling and the command-line entry point for the proposed `-encoding raw` option. Define the runtime scope and tests needed to verify that raw bytes, including 0x80, can be matched without UTF-8 conversion; done means binary-stream parsing works alongside UTF-8 parsing.

Written by the indexing model from the issue text.