Fixup -ast-print so that:

  We handle indentation of decls better.
  We Indent extern "C" { } stuff better.
  We print out structure contents more often.
  We handle pass indentation information into the statement printer, so that
  nested things come out more indented.
  We print out FieldDecls.
  We print out Vars.
  We print out namespaces.
  We indent functions better.

llvm-svn: 64232