Generated .cpp files have conversion errors: "cannot convert from 'String' to 'Float'"

When building projects for Windows targets, Haxe code which concatenates arbitrary values into strings produces invalid .cpp output with errors:

Example `.hx` input:

```
var choices = new Array();
choices.push("(" + choice + ")");
```

Resulting `.cpp` output:

```
HXLINE( 204) Float floatA = HX_("(",28,00,00,00);
HXDLIN( 204) Float floatB = ( (Float)(choice) );
HXDLIN( 204) _hx_tmp1 = (floatA + floatB);
```

Error:

```
./src/DialogTree.cpp(287): error C2440: 'initializing': cannot convert from 'String' to 'Float'
./src/DialogTree.cpp(287): note: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
```