vasnprintf-posix: Fix possible bug with negative width handling for %lc.
* lib/vasnprintf.c (VASNPRINTF): In the code for %lc in vasnprintf, test
for the FLAG_LEFT bit in the flags variable.
* tests/test-vasnprintf-posix.c (test_function): Add tests for width
given as argument for the directives %c, %lc.
* tests/test-vasprintf-posix.c (test_function): Likewise.
* tests/test-snprintf-posix.h (test_function): Likewise.
* tests/test-sprintf-posix.h (test_function): Likewise.
* tests/test-snprintf-posix.c: Include <wchar.h>, for wint_t.
* tests/test-sprintf-posix.c: Likewise.
* tests/test-vsnprintf-posix.c: Likewise.
* tests/test-vsprintf-posix.c: Likewise.