Fix some locale multibyte tests failures ad below:

Fix some locale multibyte tests failures ad below:

libc/stdlib/_strtod.c   -> tst_wcstod;
libc/stdlib/stdlib.c    -> tst_mblen, tst_mbtowc, tst_wctomb;
libc/stdio/_scanf.c     -> tst_swscanf;
libc/string/strncmp.c   -> tst_wcsncmp;
libc/misc/wchar/wchar.c -> tst_mbrlen, tst_mbrtowc, tst_wcswidth.

Signed-off-by: Filippo Arcidiacono <filippo.arcidiacono@st.com>
Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>