LLVM IR function names which disable mangling start with '\01' (https://www.llvm.org/docs/LangRef.html#identifiers).
When an identifier like "\01@abc@" gets dumped to MIR, it is quoted, but only with single quotes.
"The allowed character range explicitly excludes the C0 control block allowed), the surrogate block #xD800-#xDFFF, #xFFFE, and #xFFFF."
"All non-printable characters must be escaped. [...] Note that escape sequences are only interpreted in double-quoted scalars."
This patch adds support for printing non-printable characters between double quotes if needed.