Fix share/zoneinfo for DIRDEPS_BUILD

The tranditional build makes multiple passes through the tree.
The DIRDEPS_BUILD visits each directory only once per architecture,
thus makefiles should be able to everything they need in a single pass.

The use of TZS!= when doing make(*install*)
only works if the directory has previously been visited to do zoneinfo
since before the zoneinfo target is run TZS will be empty.

To fix this, have the zoneinfo target capture the list of files to
zoneinfo, and install-zoneinfo use that list.
Rename that target to zonefiles - since that is now what it does.

This is more efficient - we only gather the list of zones when it is
likely to have changed, and allows the makefile to do everything in a
single pass.

Reviewed by: stevek
Differential Revision: https://reviews.freebsd.org/D42624

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Update/fix Makefile.depend for userland

DIRDEPS_BUILD: Reduce restaging here.

This also fixes meta tracking for the beforeinstall since it had been
marked .PHONY before (in bsd.sys.mk).

Sponsored by: EMC / Isilon Storage Division

dirdeps.mk now sets DEP_RELDIR

Updated dependencies

Sync FreeBSD's bmake branch with Juniper's internal bmake branch.

Requested by: Simon Gerraty <sjg@juniper.net>