Rename std.string.toStringz?

[kenji hara]

> 1. Keep toStringz as it is (as well as toUTF16z) and either consider stringz
> to be some sort of word unique to the D community or just admit that we're not
> going to camelcase it because it would break too much code to do so.

++vote, but not all.

Currently, the return type of toStringz is "zero-termniated UTF-8",
not "C-string".

The 'C-string' word has multiple meanings=encodings. ASCII, Latin-1,
EUC, Shift-JIS (in Japan), UTF-8 (Linux?), UTF-16 (in Windows) ...
It depends on context.

But, maybe, many of ’C-string' equals to "zero-terminated UTF-8' or
"zero-terminated UTF-16".
Other encodings should be supported by another module (std.encoding?
Is it living?).

My proposal:
1. Add three aliased types.
    alias immutable(char)* stringz;       // useful in Linux
    alias immutable(wchar)* wstringz;  // useful in Windows
    alias immutable(dchar)* dstringz;   //
2. Rename current toStringz to toUTF8z, and add deprecated aliasing
'toStringz' to keep compatibility.
    (Adding toUTF32z in std.string module will increase consistency.
Templated toUTFXXz family is more better.)
3. std.conv.to support conversion from 'any string type' to
(|wd)stringz type (by using toUTFXXz family).

The main point is we should make the aliased type names as 'De facto'
type names, like string, wstring, dstring. (Remember the three string
types are aliased type in fact.)

We can treat the type name uint as 'unsigned int'. Because it is just
built-in type name!

User defined type names shoude be camel cased usually in D.
Then, let's make them built-in! Therefore we can remove camel cased
names from our choices.

I think this proposal is usefulness, keeping compatibility, and consistent.

Kenji