refactor: install as library files and caller script.

* build-aux/larch, lib/larch/from.lua: Remove. We no longer need
to compile a single executable from library sources.
* local.mk: Adjust.
* lib/specl/formatter/progress.lua, lib/specl/formatter/report.lua,
lib/specl/formatter/tap.lua, lib/specl/inprocess.lua,
lib/specl/loader.lua, lib/specl/main.lua, lib/specl/matchers.lua,
lib/specl/runner.lua, lib/specl/shell.lua, lib/specl/util.lua:
Manually unroll `from` macro calls, which are no longer expanded
by larch.
* specl.in: New in-tree wrapper script.
* bin/specl: Much simplified wrapper, now checked in.
* specs/specs.mk: Adjust accordingly.
* lib/specl/main (optspec): Move from here...
* lib/specl/version.lua.in: New file. ...to here, where @AUTOCONF@
variables can expanded.
* configure.ac (AC_CONFIG_FILES): Add lib/specl/version.lua, and
specl,
* .gitignore: Remove bin.  Add specl and lib/specl/version.lua.
* AUTHORS: Remove references to local stdlib.
* NEWS: Update.

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