fixed #13606/#13607 - consistently print (precise) float as such in ValueFlow debug output

[firewave]

No description provided.

[firewave]

Okay. This appears to be a bit of a mess.

#include <iostream>
#include <string>

void print(double d)
{
    std::cout << std::to_string(d) << std::endl;
    printf("%f\n", d);
    std::cout << d << std::endl;
    printf("%e\n", d);
    printf("%g\n", d);
}

int main()
{
    double d = 0.0000001;
    print(d);
    d = 1 / 0.5;
    std::cout << std::endl;
    print(d);
}

0.000000
0.000000
1e-07
1.000000e-07
1e-07

2.000000
2.000000
2
2.000000e+00
2

https://godbolt.org/z/PK7MrYqbP

std::to_string() uses %f - lacks precision
std::cout uses %g - lacks the decimal representation if it is exactly an integer not indicating it is a float

[firewave]

We should probably also add some unit tests testing this.