-nptl: Use <support/check.h> facilities in tst-setuid3
- posix: Use <support/check.h> facilities in tst-truncate and tst-truncate64
- ungetc: Fix backup buffer leak on program exit [BZ #27821]
- ungetc: Fix uninitialized read when putting into unused streams [BZ #27821]
- Make tst-ungetc use libsupport
- stdio-common: Add test for vfscanf with matches longer than INT_MAX [BZ #27650]
- support: Add FAIL test failure helper
(cherry picked from commit 7b1f3d1a6f77908bbb340b0657f1a6fd37288d44)
