eval: require stdlib explicitly.

* lib/zemacs/eval.lua, lib/zz/eval.lua: Don't rely on a global
`std` symbol from bin/zemacs or bin/zz, because we need to run
eval functions separately.  Add explicit `require "std"`.
* lib/zemacs/keymaps.lua, lib/zemacs/mkdotzemacs.lua,
lib/zemacs/zlisp/file.zl, lib/zemacs/zlisp/search.zl,
lib/zile/FileString.lua, lib/zile/file.lua,
lib/zile/keycode.lua, lib/zile/macro.lua,
lib/zile/term_curses.lua, lib/zile/term_minibuf.lua,
lib/zile/window.lua, lib/zz/commands/buffer.lua,
lib/zz/commands/search.lua, lib/zz/commands/window.lua,
lib/zz/eval.lua, lib/zz/keymaps.lua, lib/zz/mkdotzz.lua: Don't
rely on global std having been set.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
specl: clean-up now that Specl 12 is in the wild.

* bootstrap.conf (buildreq): Cite release url for Specl 12
rockspec.
* .travis.yml: Regenerate.

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