In Rgui for Windows, this.path() works by looking at the windows
handles belonging to that R process.

For an open script, the windows handle will end with " - R Editor" OR
ANY SUPPORTED TRANSLATION INTO ANOTHER LANGUAGE . For a new script, the
windows handle will be "Untitled - R Editor", again possibly translated
into another language.

What we do in "write_r_editor_regexp.R" is:

  * launch a new Rgui process in each supported language

  * open an existing script and grab the translations of " - R Editor"
    in that language

  * open a new script and grab the whole windows handle

This process is automated by a bot that moves the mouse for us,
clicking all the appropriate buttons and typing all the necessary
inputs.

We will then save that information into files "r_editor_regexp.txt" and
"untitled.txt".

In "main.R", we run "write_r_editor_regexp.R" for both ucrt and
non-ucrt R sessions (since the translations are different between the
two).

In "testing_coordinates.R", we make sure that the bot is actually
moving the mouse to the correct locations and clicking the right
buttons.
