LGTM, I didn't scan for omissions but the ones in the patch look right to me. I sort of wish we had a shorter macro as CppAsString2() get's pretty verbose when used frequently like this.
I don't quite understand the etymology of the name (it's some variation on C++'s std::to_string, plus...something), but if I did, I'd probably find the name less icky.
STR(), C_STR(), STRING(), and CSTRING() all seem to be available...