[PATCH 3/4] msvcp90: Define basic_string for runtime_error when not msvcirt.

[Daniel Lehman]

> why do you need it? The class should be not used/exported in msvcirt.

Ah, I don't need it.  the existing runtime_error functions are individually #ifndef _MSVCIRT like the rest that are exported by msvcirt, and I admittedly hadn't noticed that it wasn't exported by msvcirt.  Could the whole runtime_error just be #ifndef _MSVCIRT?

Thanks
daniel