* libio.h (_IO_LOCK_T): Handle glibc 2 when _IO_MTSAFE_IO is
        not defined.

        * iovsscanf.c (vsscanf): Make it weak alias of _IO_vsscanf if
        __linux__ is defined instead of __ELF__

        * config/linuxlibc1.mt (USER_INCLUDES): Add libio.h.
OK'd by Ulrich.

From-SVN: r16151