travis: adjust .travis.yml for zemacs name change.

* .travis.yml (script): use zemacs throughout.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
specs: be sure to set batch_mode flag before first use.

* lib/zemacs/specs/spec_helper.lua (edit): Be sure to set the
batch_mode flag before calling mkmacro/mklisp functions that
require it.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
specs: add specifications for point, point-max and point-min.

* lib/zeemacs/specs/zlisp_buffer_spec.yaml: Specify behaviour of
`point`, `point-max` and `point-min` lisp functions.
* lib/zemacs/specs/specs.mk (specl_SPECS): Add
lib/zeemacs/specs/zlisp_buffer_spec.yaml.
* lib/zeemacs/default-bindings-el.lua (global-set-key): Add
missing \M-gc binding for goto-char, required by new specs.

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