Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Pull up fixes to allow building tests along scripts and data files.

MFC of the following into stable/10:
- r257095 Allow mixing bsd.files.mk with bsd.subdir.mk.
- r258095 Allow this (bsd.progs.mk) to work with fmake.
- r258330 Need to also test for defined(${v}_${PROG}) in bsd.progs.mk.
- r259209 Make bsd.progs.mk work in directories with SCRIPTS but no PROGS.

This is all 'make tinderbox' clean as run on ref10-amd64.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Make sure the only thing that follows .endif or .else is a comment.

Drop support for COPY, -c has been the default mode of install(1)
for a long time now.

Approved by: bde

Try really hard to fix parallel installs. Add a bunch of .ORDER
directives to ensure that all realinstall sub-tasks are executed
after beforeinstall, similarly ensure that all afterinstall sub-
tasks are executed after realinstall. Demonstration:

all: task1 task2
.ORDER: task1 task2

task2: task2_subtask
.ORDER: task1 task2_subtask

task1 task2 task2_subtask:
@sleep `jot -r 1 0 1.0`
@echo ${.TARGET}

Without the second .ORDER directive, task2_subtask can be run in
parallel with task1.

Spotted by: Andrea Campi <andrea@webcom.it>

Reimplement FILES support using bsd.files.mk with the
same set of features as in recently added bsd.incs.mk
(FILESGROUPS, accessibility from both bsd.prog.mk and
bsd.lib.mk, de-pessimized typical installation path,
etc.) New standard targets: buildfiles, installfiles,
and files (buildfiles + installfiles).