Implement eval-in-namespace.

* namespace.el (namespace-eval-in-namespace): New.
(namespace--progn): Record internal symbols.
(namespace--add-internal, namespace--internal-fsyms)
(namespace--fsyms-to-csyms): New helpers.
(namespace--define): Clear out internal symbols.
(namespace-resolve): Intern qsyms for now.
(namespace--qsym-to-csym): Use namespace--internal-p instead of
namespace-resolve.
(namespace--defun-like, namespace--defstruct-options)
(namespace--slot-aliases): Work with qsyms instead of csyms.
(namespace-global): Also work for non-macros.

* namespace-test.el (test-a.5): New test.

* namespace-srcloc.el (eval-last-sexp): New command.
(eval-sexp): New helper.
([namespace] namespace): New.
(guess-namespace): Use namespace--find-name to validate guess.

* Makefile (ELFILES, ELCFILES): New vars.