std.conv.to!string(float) Is too heavy

[Hipreme]

I have wrote a simple hello world using std.conv:


```
import std.conv:to;
import std.stdio;

export void MAIN(float b)
{
	writeln("Hello World " ~ to!string(b));
}
```

Building that with dmd app.d -lib creates 500KB lib
With `-g`, it goes up to 800KB

Using ldc, the build time goes up by 2 times.

if you simply change from `float b` to `int b`, the lib goes down 
from 500KB to 60KB.
The build times decreases by almost 10x (must check), but I can 
feel that anyway.

Using std.conv greatly degrades a modularized workflow, by 
increasing a lot of build time and binary size. I needed 
implementing my own to! function to get a much better build time 
for my program.