Fix mangling for C++ namespaced types

+ setup.py instructions for Visual C++ compiler

Add setup.py openMP instructions for Microsoft Visual C++ compiler

"ustring!s" (i.e. str(ustring)) is actually not safe to optimise away for f-string formatting in Py2 as it can fail to encode the Unicode string to a byte string. And it's unlikely to appear in practice.

Fix timestamps option to work when generating a C++ output file.

writing output file to a specified location.

This posed an issue when the type parameter was a typedef.

Implemented Smith's method, which avoid overflow for all but
the most extreme exponents. This agrees with what is used in NumPy.

avoid useless formatting operations when we know at compile time that the result is a Unicode string

implement somewhat useless but obvious and straight forward string conversion of the C error return type

replace dead left-over code by the actually intended fast bint->True/False formatting implementation