* libio/Makefile (routines): Add wmemstream. (tests): Add tst-memstream1, tst-memstream2, tst-wmemstream2, and tst-wmemstream2. * libio/tst-memstream1.c: New file. * libio/tst-memstream2.c: New file. * libio/tst-wmemstream1.c: New file. * libio/tst-wmemstream2.c: New file. * libio/memstream.c (_IO_mem_sync): Remove useless call to _IO_default_sync.