Remove unused `indent_length`.
Pull some of the path handling code out of actions.cpp.
Rename path_details to path_parameter.
Rename structs and variables for include paths.
Rename input_path.?pp to native_text.
Rename input_ strings and functions.
Remove note about 'stream' strings.

Have been using a stream wrapper which uses UTF-8.
Start 1.7
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
}}}