vasnprintf-posix: handle large precision via %.*d * lib/vasnprintf.c (VASNPRINTF): Don't pass precision to snprintf when handling it ourselves. * tests/test-vasnprintf-posix.c (test_function): Add test. * tests/test-snprintf-posix.h (test_function): Likewise. * tests/test-sprintf-posix.h (test_function): Likewise. * tests/test-vasprintf-posix.c (test_function): Likewise. Reported by Alain Guibert. Signed-off-by: Eric Blake <ebb9@byu.net>