Scan CID 60023).
* libc/ctype/iswalpha.c (iswalpha): Add bounds check to avoid
out-of-bounds read from utf8 tables (CID 59949).
* libc/locale/ldpart.c (__part_load_locale): Add 1 byte to size of lbuf.
Write NUL into the last byte to accommodate split_lines (CID 60047).