Namespace aware eldoc.

* namespace-tools.el (eldoc, arglist, symbol-at-point)
(function-symbol-at-point, function-name-at-point): New.
(activate): Set eldoc-documentation-function.
([advice] function-called-at-point): Add
advice to make it namespace aware.
* namespace.el (namespace-resolve): Don't intern non-existing
symbols.
Don't allow defadvice inside of define-namespace

* namespace.el ([rewriter] defadvice): Signal error.
Fix bugs in last few commits.

* namespace-tools.el: Require 'eldoc
(symbol-at-point): Deleted.

* namespace.el (namespace--defstruct-options): Use
namespace--intern instead of namespace-resolve.