slingshot: sync with upstream.

Fix the annoying contest.sed file dropping bug.
* slingshot: Sync with upstream.
* bootstrap: Sync with slingshot.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
maint: be consistent with 'Written by' attributions.

* bin/zmacs, bin/zz: Attribute Reuben.
* lib/zmacs/zmacs.in, lib/zz/zz.in: Move 'Written by' to top in
line with other files' layout.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
configury: remove write bit on generated files.

* configure.ac (AC_CONFIG_FILES): In addition to adding an
execute bit to lib/zmacs/zmacs and lib/zz/zz, remove the write
bit from all generated files to prevent accidental editing.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
configury: re-enable './configure; make; sudo make install` mode.

* bin/zmacs, bin/zz: Reset LUA_INIT and LUA_INIT_5_2 before
re-execing with $LUA.
Also, if @datadir@ has been substituted with a real filepath,
add it to LUA_PATH before re-execing.
* lib/zmacs/zmacs.mk (lib/zmacs/commands.lua): Reset LUA_INIT
and LUA_INIT_5_2 before running zlc.
* local.mk (install_exec_hook, install-exec-hook): Support per-
editor install-exec-hook rules.
* lib/zmacs/zmacs.mk (zmacs-install-exec-hook): Substitute
for @datadir@ after 'make install' so that zmacs can find its
Lua sources.
* lib/zz/zz.mk (zz-install-exec-hook): Likewise.
* lib/zmacs/zmacs.in, lib/zz/zz.in: Improve wrapper comment.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>