[Bug preprocessor/82506] Stringizing raw string literals

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82506

--- Comment #1 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
We fail to stringize raw string literals containing \n chars:
./xg++ -B./ q.cc -E  
gives:

"R\"(
)\""

(snipping line markers).  That's a regular string literal with a naked LF char
in it.  This is like the recent fix for __FILE__ dying with filenames
containing LF.