Does C support raw string literals?

Does C have such a thing? If so, in what version of the standard? C11?

C (C90, C99, C11) does not support this feature or any other similar feature.

If not, does anyone know if it is being planed

I have no idea, but usually there is a strong resistance of C committee to include new features in C.

and if any compilers support it?

I just tested it and it is apparently supported with recent gcc versions as a GNU extension (compile with -std=gnu99 or -std=gnu11).

For example:

printf(R"(hello\nworld\n)");

compiles and gives the expected behavior.