Rename id_manager to document_state.

[SVN r86635]
Remove `document_root` member from `file_info`.

It isn't actually used any more.

[SVN r86636]
Make member_action and friends available in actions.

A fairly clumsy mechansim for calling member functions in parsers.

[SVN r86637]
Document the element flags and masks a bit better.

I'm considering how source_mode tags work for paragraphs, which touches
on the contextual block stuff, so I wanted to clarify it.

As always, contains some TODOs that might not ever be dealt with.

[SVN r86638]
Use a slightly clearer name for the grammar's block mask.

[SVN r86639]
Store source mode as tag rather than string.

[SVN r86640]
Remove unused `indent_length`.

[SVN r86641]
Pull some of the path handling code out of actions.cpp.

[SVN r86642]
Rename path_details to path_parameter.

[SVN r86643]
Rename structs and variables for include paths.

[SVN r86644]
Rename input_path.?pp to native_text.

[SVN r86645]
Rename input_ strings and functions.

[SVN r86646]
Remove note about 'stream' strings.

Have been using a stream wrapper which uses UTF-8.

[SVN r86647]
Don't disable the newline after block handler in 1.7.

It isn't needed, although it does mean that this might be surprising:
{{{
* xxx xxx xxx
xxx xxx xxx
[block]
yyy yyy yyy
}}}

which is now equivalent to:

{{{
* xxx xxx xxx
  xxx xxx xxx

  [block]

yyy yyy yyy
}}}

[SVN r86648]