Fix printf(1) ignores width and precision in %b format.

The precision with the conversion specifier b is specified by POSIX: see
point 7 in the reference documentation.

This corrects previous wrong log in r337440.

Reference: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/printf.html

PR: 229641
Reported by: Rudolf Cejka
Submitted by: Garrett D'Amore (illumos)
MFC after: 1 week