Turns out mt.isinf is happy to accept non-primitive floats (such as
CsvFloat) as long as __float__ is defined. But CsvInt expects a float
inf, not a CsvFloat, so things explode later.
Fixed by explicitly casting to float if mt.isinf, instead of passing
as-is.
Also tweaked CsvInt/CsvFloat constructors to not bother checking
isinstance, unconditional int/float casts are probably cheaper than the
condition in Python.
Christopher Haster
8a4d114934