String conversion functions in Phobos

[simendsjo]

I want to convert SomeChar[] or SomeChar* into 
PerhapsAnotherCharNullTerminated*, but std.conv doesn't work like this.
char[] a = "ao";
to!(wchar*)(a); // fails

toUTF16z converts char[] to wchar*
toStringz converts char[] to char*

Am I missing function(s), or do I have to combine them myself?