(bad error message on incorrect string literal)
Fixed the error message for incorrect string literal
before:
```
test.cpp:1:19: error: invalid character '
' character in raw string delimiter; use PREFIX( )PREFIX to delimit raw string
char const* a = R"
^
```
now:
```
test.cpp:1:19: error: invalid newline character in raw string delimiter; use PREFIX( )PREFIX to delimit raw string
1 | char const* a = R"
| ^
```
---------
Co-authored-by: Jon Roelofs <jroelofs@gmail.com>
