Support all IEC 60559 types (_Float{32,64,128},_Float{32,64,128}x)

[trofi]

Hackage's ncurses-0.2.16 package fails to build against ncurses-6.1 C library as it now defines references to _Float32 and _Float64. The c2hs fails to built ncurses as:

c2hs: C header contains errors:

/usr/include/wchar.h:396: (column 17) [ERROR]  >>> Syntax error !
  The symbol `wcstof32' does not fit here.

/usr/include/wchar.h contents are:

#ifdef __USE_ISOC99
/* Likewise for `float' and `long double' sizes of floating-point numbers.  */
extern float wcstof (const wchar_t *__restrict __nptr,
                     wchar_t **__restrict __endptr) __THROW;
extern long double wcstold (const wchar_t *__restrict __nptr,
                            wchar_t **__restrict __endptr) __THROW;
#endif /* C99 */

/* Likewise for `_FloatN' and `_FloatNx' when support is enabled.  */

#if __HAVE_FLOAT16 && defined __USE_GNU
extern _Float16 wcstof16 (const wchar_t *__restrict __nptr,
                          wchar_t **__restrict __endptr) __THROW;
#endif

#if __HAVE_FLOAT32 && defined __USE_GNU
extern _Float32 wcstof32 (const wchar_t *__restrict __nptr,
                          wchar_t **__restrict __endptr) __THROW;
#endif

#if __HAVE_FLOAT64 && defined __USE_GNU
extern _Float64 wcstof64 (const wchar_t *__restrict __nptr,
                          wchar_t **__restrict __endptr) __THROW;
#endif

#if __HAVE_FLOAT128 && defined __USE_GNU
extern _Float128 wcstof128 (const wchar_t *__restrict __nptr,
                            wchar_t **__restrict __endptr) __THROW;
#endif

#if __HAVE_FLOAT32X && defined __USE_GNU
extern _Float32x wcstof32x (const wchar_t *__restrict __nptr,
                            wchar_t **__restrict __endptr) __THROW;
#endif

#if __HAVE_FLOAT64X && defined __USE_GNU
extern _Float64x wcstof64x (const wchar_t *__restrict __nptr,
                            wchar_t **__restrict __endptr) __THROW;
#endif

#if __HAVE_FLOAT128X && defined __USE_GNU
extern _Float128x wcstof128x (const wchar_t *__restrict __nptr,
                              wchar_t **__restrict __endptr) __THROW;
#endif

To clarify: gcc-8.1.0 directly supports the following types: _Float{32,64,128}, _Float{32,64,128}x (they are not typedef aliases of other types from syntax standpoint).