Basic functionality for packages

Basic functionality for packages

Lisp packages exist and can be dumped and loaded.  Two standard
packages "emacs" and "keyword".  Some package functions and variables
of CLHS.

Symbols have a package slot.  Built-in symbols before loaodup get
packages emacs or keyword.

Dumping and loading.

Some tests.

* src/pkg.c: New file for Lisp packages.
* src/Makefile.in (base_obj): Add pkg.c.
* test/src/pkg-tests.el: New file.
* src/lisp.h: Add Lisp_Package.
* etc/emacs_lldb.py: Add Lisp_Package.
* src/data.c (Ftype_of): Handle packages.
(syms_of_data): Add Qpackage.
* src/emacs.c (main): Initialize pkg.c, fix built-in symbols.
* src/fns.c (check_hash_table, get_key_arg): Make externally visible.
* src/pdumper.c (dump_vectorlike): Handle packages.
* src/print.c: Print packages, print symbols with packages.