Refactor remaining mount_* commands to use the common pathadj()
function for resolving paths.

Make pathadj() no longer warn about symlinks. Symlinks in /dev are
regularly used in several places like

Refactor remaining mount_* commands to use the common pathadj()
function for resolving paths.

Make pathadj() no longer warn about symlinks. Symlinks in /dev are
regularly used in several places like LVM . The warning was also
only visible when calling a mount_* command directly as mount(8)
itself would resolve the path witout warning before passing it to
a mount_* command.

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Move WARNS=3 to the Makefile.inc, and add a little const to the remaining
programs that did not compile before.

Kill __P(), use ANSI function declarations; WARNS=3.

move getmntopts(3) to libutil, build and install also it's manpage
bump libutil minor
adjust individual mount_*/Makefile to use libutil getmntopts(3)

Use ${NETBSDSRCDIR}/some/path instead of ${.CURDIR}/../../some/path

Add mount_overlay.