Line number is wrong when code contains multiline string literals.

Consider this Mirah code:

``` mirah
class Foo
    CONST = "a



    b"
end


ERROR_SHOULD_BE_HERE
```

When compiling, an error should happen at line 11. An error does happen, but erroneously at line 7. This means that, especially for longer Mirah code, the error messages generated by the compiler do not match with the actual code.
