[Bug c/114773] Raw string literals are not supported in C89 mode

[rl.alt.accnt at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114773

--- Comment #4 from Sirraide <rl.alt.accnt at gmail dot com> ---
Yeah, we figured that that was why they’re not supported in `-gnu89` mode, but
I thought I’d ask just to be sure.