Log Message:
mksh: Pull in the printf(1) builtin from MirBSD.

Note that we are specifically using -r1.21 as newer versions do not build.

This improves performance on systems that use mksh as the bootstrap shell, due
to widespread use of printf in the pkgsrc infrastructure that previously had
to fork /usr/bin/printf.

Tested on macOS and SmartOS.  Bump PKGREVISION.