- change ast.Ident back to contain the name and adjust all dependent code
- identifier object information will be added again through an optional
  typechecker phase (in the works).
- remove tracking of scopes in parser - it's easier to do this in a separate
  phase (in the works)
- in godoc, generate popup info table directly instead of through a formatter
  for simpler data flow (at the expense of a little bit more code)

Runs all tests.

As a result of this change, the currently shown popup information
(const, var, type, func, followed by identifier name) will not be
shown anymore temporarily.

R=rsc
CC=golang-dev
https://golang.org/cl/1994041