A weird example of .toUTF16z concatination side-effects in wcsncat

[BoQsc]

Here I try to concatenate three character strings using 
`wcsncat()`.

`clang_string`         AAAAAAAAAA
`dlang_string`         BBBBBBBBBBB
`winpointer_to_string` CCCCCCCCCC


```
import std.stdio;

@system void main(){

	import std.utf                : toUTF16z, toUTF16;
	import core.stdc.wchar_       : wcsncat, wcslen, wprintf;
	import core.stdc.stdlib       : wchar_t;
	import core.sys.windows.winnt : LPCWSTR;

	wchar_t* clang_string         = cast(wchar_t *)"AAAAAAAAAA";
	string   dlang_string         = "BBBBBBBBBBB";
	LPCWSTR  winpointer_to_string = "CCCCCCCCCC";
	
	wcsncat(clang_string, dlang_string.toUTF16z, 
wcslen(dlang_string.toUTF16z));
	//   String output: AAAAAAAAAABBBBBBBBBBB
	
	wcsncat(clang_string, winpointer_to_string, 
wcslen(winpointer_to_string));
	//   String output: AAAAAAAAAABBBBBBBBBBBBBBBBBBBB
	// Expected string: AAAAAAAAAABBBBBBBBBBBCCCCCCCCCC

	wprintf(clang_string);
	//   String output: AAAAAAAAAABBBBBBBBBBBBBBBBBBBB
	// Expected string: AAAAAAAAAABBBBBBBBBBBCCCCCCCCCC

}


```

**Problem:**
Any *following concatenated string* after "`wcsncat()` 
concatenation of `dlang_string.toUTF16z` string", happen to not 
be printed and gets overwritten.

**The Expected output:**
I was expecting the `wprintf()` **result** to be 
`AAAAAAAAAABBBBBBBBBBBCCCCCCCCCC`
The `wprintf() `  **result** I've received is this:  
`AAAAAAAAAABBBBBBBBBBBBBBBBBBBB`