WCHAR

This scanf implementation supports wide characters, but only as an optional
feature that has to be enabled separately by defining SCANF_WIDE.

The allowed values are:
* SCANF_WIDE=0: only narrow/multibyte scanf supported (default)
* SCANF_WIDE=1: only wide scanf supported
* SCANF_WIDE=2: both narrow/wide scanf supported, but no interoperability
                (%c %s %[ only for scanf, %lc %ls %l[ only for wscanf)
* SCANF_WIDE=3: both narrow/wide scanf supported, with full interoperability

Any SCANF_WIDE other than 0 requires a header called "wide.h" to define:
* wint_t, an integral type enough to store any value of wchar_t and WEOF
* WEOF, a macro representing a special value of type wint_t that does not
  correspond to any valid wchar_t in the wide character set
* scanf_mbstate_t, a type used with mbrtowc_ and wcrtomb_ (see below). not
  strictly required for SCANF_WIDE values other than 3

You can also define these to replace wchar_t altogether:
    WCHAR               (default: wchar_t)
    WINT                (default: wint_t)
    MAKE_WCHAR(c)       (default: L##c, so MAKE_WCHAR('A') => L'A')
    MAKE_WSTRING(s)     (default: L##s, so MAKE_WSTRING("ABC") => L"ABC")
but make sure your own definitions (of getwch_, etc.) use the same types.

wide.h must be provided manually, or alternatively you can pick an existing
implementation from one of the folders under "wide" folder. Note that you can
simply include some existing wide.h before you include wscanf.h; in that case,
you do not even need a wide.h in the same folder.

SCANF_WIDE=1 requires the following two functions to be implemented:

    wint_t getwch_(void);
    void ungetwch_(wint_t);

with wint_t as previously stated. These functions should work like getch_ and
ungetch_ respectively, but for wide characters. getwch_ should return WEOF
(as defined by "wide.h") for EOF, or any other wint_t value representing a wide
character (wchar_t).

SCANF_WIDE=2 also requires getch_, ungetch_.

SCANF_WIDE=3 also requires

    void mbsetup_(scanf_mbstate_t *ps);
    size_t mbrtowc_(wchar_t *pwc, const char *s, size_t n, scanf_mbstate_t *ps);
    size_t wcrtomb_(char *s, wchar_t wc, scanf_mbstate_t *ps);

mbsetup_ should reset the pointed scanf_mbstate_t into its default state.
mbrtowc_ and wcrtomb_ shall function like mbrtowc and wcrtomb, respectively, as
described in ISO/IEC 9899:1999.
(However, neither pwc, s nor ps will ever be NULL)

The wide scanf function declarations are located in wscanf.h.

Wide extensions (see EXTENSIONS) are also supported with a different signature:

    int scnwext_(wint_t (*getwch)(void *data), void *data, const wchar_t **format, wint_t *buffer, int length, int nostore, void *destination);